ADP vs. MDB: Speed
Neil
7 back end. The view is scrolling very slowly. However, if I open the view
in an ADP file, it scrolls quickly.
I needed to use an ODBC link for the view because it needs to be editable.
Otherwise, I would have used a pass-through query.
In previous discussions about using an MDB file vs. an ADP file as a front
end for SQL Server, the impression I got was that both were about the same,
but that the MDB was a more mature technology and less problematic than the
ADP technology. However, the speed difference I'm noticing with the ADP file
in regards to this view is significant and is very disconcerting re. using
an MDB file.
Any thoughts/comments/suggestions would be appreciated. I've reproduced the
view's SQL below for reference.
Thanks,
Neil
SQL for view in question:
SELECT INVTRY.[Index], INVTRY.TITLE, INVTRY.AUTHILL1,
INVTRY.attFirstEdition, INVTRY.attSigned,
ISNULL(INVTRY.attSignedPD, ' ') SignedCond, INVTRY.YRPUB,
INVTRY.PRICE, INVTRY.Web, INVTRY.Status,
INVTRY.WebStatusPending, INVTRY.ActivateDate,
INVTRY.DeactivateDate, INVTRY.WebAddedBatchID,
INVTRY.AllowDuplicate, INVTRY.WebAction,
INVTRY.WebActionPending, INVTRY.DateModified,
INVTRY.DateWebActionApplied, INVTRY.JIT, INVTRY.MImage,
INVTRY.HImage, INVTRY.AdCode,
CASE WHEN INVTRY.WebAddedBatchID IS NOT NULL
THEN - 1 ELSE 0 END AS OnWeb
FROM vwInventory_Dupes INNER JOIN
(WebStatus INNER JOIN
(INVTRY INNER JOIN
tabStatus ON INVTRY.Status = tabStatus.Status) ON
WebStatus.WebStatus = INVTRY.Web) ON
(vwInventory_Dupes.YearPub = INVTRY.YRPUB) AND
(vwInventory_Dupes.SignedCond = ISNULL(INVTRY.attSignedPD,
' ')) AND (vwInventory_Dupes.Signed = INVTRY.attSigned) AND
(vwInventory_Dupes.FirstEd = INVTRY.attFirstEdition) AND
(vwInventory_Dupes.Author = INVTRY.AUTHILL1) AND
(vwInventory_Dupes.TITLE = INVTRY.TITLE)
WHERE (((tabStatus.ForWeb) = 1) AND ((WebStatus.IncludeDupe)
= 1))
SQL for vwInventory_Dupes, used as subquery:
SELECT INVTRY.TITLE, INVTRY.AUTHILL1 Author,
Cast(attFirstEdition AS tinyint) FirstEd,
Cast(attSigned AS tinyint) Signed,
ISNULL(INVTRY.attSignedPD, ' ') SignedCond,
INVTRY.YRPUB YearPub
FROM WebStatus INNER JOIN
(INVTRY INNER JOIN
tabStatus ON INVTRY.Status = tabStatus.Status) ON
WebStatus.WebStatus = INVTRY.Web
WHERE (((tabStatus.ForWeb) = 1) AND ((WebStatus.IncludeDupe)
= 1))
GROUP BY INVTRY.TITLE, INVTRY.AUTHILL1,
Cast(attFirstEdition AS tinyint), Cast(attSigned AS tinyint),
ISNULL(INVTRY.attSignedPD, ' '), INVTRY.YRPUB
HAVING (((COUNT(INVTRY.[INDEX])) > 1))
Steve Jorgensen
the other will be faster.
By default, the MDB opens a Dynaset which means it first opens a connection to
grab the list of keys for the records, then reads the actual records as needed
for display by doing individual selects of 10 records aby explicit key. This
can help speed when each row has a lot of data because only the rows that are
actually viewd will be read, not all of them. On the other hand, if the table
has a very large number of rows, Access will spend a lot of time in the
background reading the whole list of keys, and if the key lookup for each row
is slow for some reason, everything will be sluggish.
An ADP, a static recordset is normally used, and an absolute cap of 10,000
rows is applied, so if your recordset has more than that, you just won't get
all the rows. Static means in loads all the data at once, then you browse
through it in memeory. That's very fast once you load the data, but if each
row has a lot of data, especially memo fields and such, it can take a long
time to initially load.
Sylvain Lafontaine fill the blanks, no spam please
http://support.microsoft.com/kb/q209123/
If this doesn't help, then you will have to use an unbound form coupled with
SQL pass-through queries (or ADO objects) to resolve your speed problem with
MDB. Another solution could be to go with TS to simulate a high-speed LAN.
I don't know where you got the impression that MDB were about the same as
ADP in term of speed. It has been repeated a number of times that the use
of MDB' linked tables and views is only a workable solution for small
databases on a fast Lan.
S. L.
"Neil" <njo...@pxdy.com> wrote in message
news:Uxa%d.15606$cN6....@newsread1.news.pas.earthlink.net...
Steve Jorgensen
the blanks, no spam please)> wrote:
>You may try to add a virtual index on your linked view:
>http://support.microsoft.com/kb/q209123/
>
>If this doesn't help, then you will have to use an unbound form coupled with
>SQL pass-through queries (or ADO objects) to resolve your speed problem with
>MDB. Another solution could be to go with TS to simulate a high-speed LAN.
>
>I don't know where you got the impression that MDB were about the same as
>ADP in term of speed. It has been repeated a number of times that the use
>of MDB' linked tables and views is only a workable solution for small
>databases on a fast Lan.
Frankly, I find that statement ludicrous. Many developers including myself
have had excelent results using MDBs as front-ends to various kinds of SQL
Server back-end for many years before there was such a thing as an ADP. When
MDBs are slow, the workarounds to fix it are far less arduous than the
workarounds required in ADPs to simply make them function in many cases.
Neil
> http://support.microsoft.com/kb/q209123/
Yes, these are added when you first attach the view or table. When the
object doesn't have a primary key (as with views) Access prompts you for
which field(s) to use as pk. It then stores that information. You can't
update the data otherwise. So it's already there.
> If this doesn't help, then you will have to use an unbound form coupled
> with SQL pass-through queries (or ADO objects) to resolve your speed
> problem with MDB.
As noted, the reason for not using pass-through is because it needs to be
updatable.
>Another solution could be to go with TS to simulate a high-speed LAN.
What is "TS"?
> I don't know where you got the impression that MDB were about the same as
> ADP in term of speed. It has been repeated a number of times that the use
> of MDB' linked tables and views is only a workable solution for small
> databases on a fast Lan.
From discussions in this newsgroup.
Neil
Neil
number here. And only returning 24 fields.
There was a modification recently where three additional fields were added
to the view, and that seemed to slow things down significantly. I'm not sure
if there's some boundary at around 24 fields, or if something else is going
on. But the linked view is *very* slow, taking several seconds just to bring
up the first screen, and then, whenever the scroll bar goes down by one,
several more seconds just to refresh. The ADP view, on the other hand, is
fast, with no delay at all, either in bringing up the data or in scrolling.
Neil
"Steve Jorgensen" <nos...@nospam.nospam> wrote in message
news:kq9r31tdjl3tv8v10...@4ax.com...
Sylvain Lafontaine fill the blanks, no spam please
getting a multi-user access to an Access' MDB file over the Internet or to
solve the possibility of corruption when you LAN network is not rock solid.
However, this solution come with a price ($).
With the use of unbound forms as the solution, you are responsible for
sending the modifications to the data back to the database. This will give
you the possibility to use the result of a read-only SQL pass-through in a
form but, obviously, with the obligation of having more coding work to be
done. Of course, some of this work can be partially automated. You will
find more information on that subject on books dealing with Access and
SQL-Server. (Personally, I prefer to use ADP but it has many bugs.)
By using the profiler on the SQL-Server, it is also possible that you will
see something that will give you the possibility of resolving the speed
problem of you linked views by having a better understanding of what Access
is doing when it communicates with the server.
S. L.
"Neil" <njo...@pxdy.com> wrote in message
news:FCk%d.633$H06...@newsread3.news.pas.earthlink.net...
Sylvain Lafontaine fill the blanks, no spam please
In the case of the WAN, all tests that I have done in the past indicate that
MDB files are much slower to access a SQL-Server backend. The use of linked
views will greatly reduce the performance hit but even with them, I don't
see the benefice of creating hundred of views instead of creating hundred of
stored procedures. If you want to get some decent speed over the internet,
there are a lot more of work to do using MDB than using ADP and even then,
I'm not really sure if the use of linked views will achieve the same level
of performance.
You are entitled to your opinion but all the tests that I have done in the
past clearly indicate that the use of MDB to access a SQL-Server over the
internet is only, at its best, a kludge.
For a LAN, the problem is of course much less severe but at the condition
that the network is not already overcrowded.
S. L.
"Steve Jorgensen" <nos...@nospam.nospam> wrote in message
news:vvgr31l3buv11blqb...@4ax.com...
Steve Jorgensen
view when you created the link? If not, it will be slower, and will not be
updateable.
Steve Jorgensen
it was particularly appropriate to connect directly to a database server
across a WAN at all. I usually recommend using a terminal server or rewriting
the app as a Web application or some other kind of 3-tier application.
On Sun, 20 Mar 2005 16:49:55 -0500, "Sylvain Lafontaine" <sylvain aei ca (fill
Albert D. Kallal
news:Uxa%d.15606$cN6....@newsread1.news.pas.earthlink.net...
>
> end for SQL Server, the impression I got was that both were about the
> same, but that the MDB was a more mature technology and less problematic
> than the ADP technology. However, the speed difference I'm noticing with
> the ADP file in regards to this view is significant and is very
> disconcerting re. using an MDB file.
>
> Any thoughts/comments/suggestions would be appreciated. I've reproduced
> the view's SQL below for reference.
Yes, a few things needs to cleared up here.
First, using a ADP with sql server is kind of like using a automatic truck
vs a truck with a standard shift. If you don't know trucks, and how to shift
gears, then obviously the automatic truck is going to be better. On the
other hand, an advanced driver will get the same performance out of the
standard truck....
If you look at the sql you posted, there is a number of tables involved.
If you just link a bunch of tables to sql server, and then tell ms-access to
"join" them together..you will often get poor performance. I mean, obviously
ms-access/JET has to pull data from multiple tables. With ODBC linked
tables, each table is *often* thought as a separate data source. With
a ADP, that sql is processed server side.
Remember, ms-access/JET has a difficult
time working with multiple ODBC DATA sources when you do a join on them. The
reason of course is that one table might be from Oracle, and the other might
be a local FoxPro table. When you join data through linked tables, you have
to remem ber what the Robot in Lost in space used to say:
"Danger ...Will Robison.....Danger"...
When you use a ADP, that whole sql statement is sent to sql server to be
processed.
So, of course, if you used a pass-through query, then both the ADP, and the
ODBC will performance the same.
However, you mentioned that you can't use a pass through. However, you STILL
are using a sql statement that have SEVERAL LINKED tables. ms-access is
going
to have to figure out those links for you!. This should not be a surprise if
you think about what is going on here. However, the simple solution here is
thus to simply create a view on sql server, and then link to that!
Doing this, you will get the same
performance again as the ADP.
So, the lesson here is that you simply have to be MORE conscience of sql
that joins tables together. You can often get away with at last one extra
joined table via link tables..but as a general rule, you have to build a
query
anyway, so, just built a view on the sql side..and you eliminate the
performance
problem.
So, our question is using a ADP going to be faster then a MDB with linked
tables?
answers: Yes, ADP will be faster if you don't pay attention to avoiding
bottle necks, and thinking about what is going on....
So, yes, you do need a bit more caution when using a mdb file and odbc
tables against sql server. Without question, a ADP allows you to be much
more lazy, as ALL
SQL is 100% executed on the sql server side, and thus it is MUCH harder to
screw things up. With a mdb/odbc linked tables, you need extra caution, and
extra effort to avoid bottle necks. In effect, the increased flexibility of
a
mdb/odbc setup means you have more rope and more room to hang yourself!!
However, with a small effort, and some caution, you can EASLEY get the same
performance with a mdb/odbc as you get with a
ADP.
--
Albert D. Kallal (Access MVP)
Edmonton, Alberta Canada
pleaseNOO...@msn.com
http://www.members.shaw.ca/AlbertKallal
Albert D. Kallal
> Are you talking about the WAN or a LAN?
>
> In the case of the WAN, all tests that I have done in the past indicate
> that MDB files are much slower to access a SQL-Server backend.
The problem of slowness is not ms-access/jet, but that how the developer
uses sql server here.
When ms-access is used correctly, and thoughtfully by a developer, then the
limits of the application become that of sql server, and not ms-access at
al. There are companies out there with 1000 simultaneous ms-access users
hitting the same sql server database. using ms-access is no worse the using
VB6, c++ or any other ide. The ONLY differences here are that of poor
developers.
> The use of linked views will greatly reduce the performance hit but even
> with them, I don't see the benefice of creating hundred of views instead
> of creating hundred of stored procedures.
HUH? You mean grabbing data from a link view vs a stored proc makes any
difference here? (it makes not ONE bit!!).
If you talking about some code that needs to update some data..then, sure,
by all means move the code from ms-access into a stored proc, but we are not
talking about bad development practices here.
Without question, execute sql on a JET based client through linked tables
needs caution. ANY time more then one table is involved, that sql should be
put on the server side, or pass through be used. If one follows this rule,
then 9 out 10 times, the odbc linked application will perform as good as the
ADP one.
The fact of the matter is that a native ole-db connection sql server vs a
odbc one has be thrashed out MANY TIMES. If I hit a database and ask the sql
server to return one record, both the ole-db, and a simply linked table in
ms-access both return one record, and produce approximate the same network
traffic.
> If you want to get some decent speed over the internet, there are a lot
> more of work to do using MDB than using ADP and even then, I'm not really
> sure if the use of linked views will achieve the same level of
> performance.
Linked views is the solution in this poster case. If the poster does this,
then no difference will be noticed. The problem here is not ms-access, but
users of ms-access who don't take the time to utilize, and effect use sql
server here.
>
> You are entitled to your opinion but all the tests that I have done in the
> past clearly indicate that the use of MDB to access a SQL-Server over the
> internet is only, at its best, a kludge.
Compared to what? I know of people successfully using ms-access OVER DIAL UP
lines to sql server (you read that correctly!!). If you make the effort,
(and this is NO more effort then writing in VB6, or other tools, then you
get the same performance).
So, sure, if a person just lazily links multiple tables..and then tries to
build a local query based on all those linked tables..then you will not get
decent performance.
However, it is a myth that a ms-access odbc connection to sql server don't
work well. It will JUST as well as the other IDE's, and you get the same
performance....
Further, bound forms in ms-access can successful be used, but again, as long
as stupid things like opening a form to a table without some type of "where"
clause must be avoided. (I never do that in JET based solutions...let alone
sql server based ones anyway).
Again, the fact that SO many ms-access applications open up forms to a
table, and THEN let the user browse/search for a record is a HORRIBLE
design, and one that should be avoided.
So, it is not the fact of ms-access being bad, but the fact that it is SO
EASY to simply throw up a form with a large data set, and let the user "have
at it".
So, even bound forms can quite well be used over a wan.
The real problem here is bad practices...not ms-access...
Sylvain Lafontaine fill the blanks, no spam please
telling me that if I forget about 90% (or 50, 60 or 70%, pick your number)
of the coding facilities of SQL-Server, I will be a better programmer?
I know that the use of linked views will provide some relief about the lack
of speed of linked ODBC tables; however, I don't see why this could be
considered as an advantage:
1) It will take as much time creating all the necessary views for each
form/sub-form/control using a join in their queries than it will take for
creating the relevant stored procedures.
2) When I will really need to use a stored procedure - for example for
having access to temporary tables, cursor, other stored procedures, etc. -
because of the underlying complexity of the request, I will have a pretty
leg if I've limited myself to the exclusive use of views because I'm using
ODBC linked tables.
(For obvious reasons, I won't comment on the possibility of using a sql
pass-through query in these cases.)
From what I can read from your post, it's like telling me that a car is as
good and as fast as another one for the same price, but that you have the
right to go in only half the city if you buy it. In my opinion, when you
have to pay the same price in working time (at the minimum), you should be
entitled to the same full capacity in programming capabilities and when the
price is higher, there should be more, not less, capabilities.
I don't see why limiting myself to the exclusive use of views and forgetting
about stored procedures will make me a better programmer but I you want to
go on this path, this is your right and your decision; not mine.
S. L.
"Albert D. Kallal" <kal...@msn.com> wrote in message
news:FYn%d.745819$8l.276231@pd7tw1no...
Neil
"Steve Jorgensen" <nos...@nospam.nospam> wrote in message
news:fnvr3110nfld0dami...@4ax.com...
Neil
difference is the same. So there isn't a WAN vs. LAN issue anyway. FWIW.
Neil
"Steve Jorgensen" <nos...@nospam.nospam> wrote in message
news:1svr31tgrv6q82ilc...@4ax.com...
Neil
Perhaps you misread my original post, since you wrote:
"The problem of slowness is not ms-access/jet, but that how the developer
uses sql server here."
And:
"ANY time more then one table is involved, that sql should be put on the
server side, or pass through be used. If one follows this rule,
then 9 out 10 times, the odbc linked application will perform as good as
the ADP one."
And:
"Linked views is the solution in this poster case. If the poster does this,
then no difference will be noticed."
I say that you must have misread my original post, since linked views are
what are being used here; yet you offer them as a solution.
From my original post:
"I have a situation with an ODBC linked view in an Access 2000 MDB...."
Neil
"Albert D. Kallal" <kal...@msn.com> wrote in message
news:FYn%d.745819$8l.276231@pd7tw1no...
Neil
"Sylvain Lafontaine" <sylvain aei ca (fill the blanks, no spam please)>
> TS = Terminal Server; you can also use Citrix. This is a quick fix for
> getting a multi-user access to an Access' MDB file over the Internet or to
> solve the possibility of corruption when you LAN network is not rock
> solid. However, this solution come with a price ($).
Not an issue with connection. I'm using the db locally for development with
MSDE and have the same situation with the linked view being slow. Definitely
not a network issue.
>
> With the use of unbound forms as the solution, you are responsible for
> sending the modifications to the data back to the database. This will
> give you the possibility to use the result of a read-only SQL pass-through
> in a form but, obviously, with the obligation of having more coding work
> to be done. Of course, some of this work can be partially automated. You
> will find more information on that subject on books dealing with Access
> and SQL-Server. (Personally, I prefer to use ADP but it has many bugs.)
Yes, I'm familiar with the approach. It would just be better to save the
development overhead. And, if one were to use unbound forms, then one might
as well just use VB.
>
> By using the profiler on the SQL-Server, it is also possible that you will
> see something that will give you the possibility of resolving the speed
> problem of you linked views by having a better understanding of what
> Access is doing when it communicates with the server.
Yeah, perhaps. The strange thing, as noted elsewhere in this thread, is that
it was fine until I added three new fields. So I don't know if something
needs to be optimized, or going from 21 to 24 fields really makes that much
of a difference.
Neil
> If you just link a bunch of tables to sql server, and then tell ms-access
> to
> "join" them together..you will often get poor performance.
Again, as noted in my other post, you misread my original post. The first
sentence in my post stated I was dealing with a linked view, and, before the
SQL I posted I said it was the view's SQL. The SQL is from a SQL view --
pure server side -- nothing done in Access except to link to the view and
display the data.
> However, you mentioned that you can't use a pass through. However, you
> STILL
> are using a sql statement that have SEVERAL LINKED tables. ms-access is
> going
> to have to figure out those links for you!. This should not be a surprise
> if
> you think about what is going on here. However, the simple solution here
> is
> thus to simply create a view on sql server, and then link to that!
Which is what was done.
>
> Doing this, you will get the same
> performance again as the ADP.
Well, this gets us back to the original post: that is what was done; yet the
linked view in the MDB file is sluggish, taking a long time to scroll, and
the same linked view in the ADP file is quick. Both the MDB and ADP are
accessing a single view from SQL Server.
> So, the lesson here is that you simply have to be MORE conscience of sql
> that joins tables together. You can often get away with at last one extra
> joined table via link tables..but as a general rule, you have to build a
> query
> anyway, so, just built a view on the sql side..and you eliminate the
> performance
> problem.
Apparently not -- at least not in this case.
In *theory* a view from SQL Server should perform the same in an ADP and
MDB, since the processing is done on the server side. But, as this situation
demonstrates, things are not always as simple as they appear in theory.
Oh, and before we go there, please note that the large-recordset issue has
already been addressed: there are only 1154 records returned by the view,
with 24 fields displayed.
>
> So, our question is using a ADP going to be faster then a MDB with linked
> tables?
>
> answers: Yes, ADP will be faster if you don't pay attention to avoiding
> bottle necks, and thinking about what is going on....
>
> So, yes, you do need a bit more caution when using a mdb file and odbc
> tables against sql server. Without question, a ADP allows you to be much
> more lazy, as ALL
> SQL is 100% executed on the sql server side, and thus it is MUCH harder to
> screw things up. With a mdb/odbc linked tables, you need extra caution,
> and
> extra effort to avoid bottle necks. In effect, the increased flexibility
> of
> a
> mdb/odbc setup means you have more rope and more room to hang yourself!!
>
> However, with a small effort, and some caution, you can EASLEY get the
> same
> performance with a mdb/odbc as you get with a
> ADP.
Well, I'm open to suggestions!
Neil
Sylvain Lafontaine fill the blanks, no spam please
and are Invtry.MImage and Invtry.HImage image (binary) fields?
Second, you should really take a look with the profiler. Don't forget that
we don't have your database in front of us and that it is quite possible
that only you will have the possibility of solving this problem.
S. L.
"Neil" <njo...@pxdy.com> wrote in message
news:w9s%d.1003$H06...@newsread3.news.pas.earthlink.net...
Neil
field was AdCode, which is varchar.
"Sylvain Lafontaine" <sylvain aei ca (fill the blanks, no spam please)>
wrote in message news:eS2v9bdL...@tk2msftngp13.phx.gbl...
Sylvain Lafontaine fill the blanks, no spam please
give something.
S. L.
"Neil" <njo...@pxdy.com> wrote in message
news:lFt%d.109$gI...@newsread1.news.pas.earthlink.net...
Trevor Best
> MImage and HImage are two of the new fields, and are bit. The other new
> field was AdCode, which is varchar.
May not have anything to do with speed and you may have already done
this but with bit fields, make sure they are "not null" and default to 0.
--
This sig left intentionally blank
Albert D. Kallal
>I don't really understand your statement about poor developers: you are
>telling me that if I forget about 90% (or 50, 60 or 70%, pick your number)
>of the coding facilities of SQL-Server, I will be a better programmer?
No, all I am saying is that if a developer uses good designs, and good
practices, then good performance will result. My only point here is that
some things such as building join queries ACROSS linked tables is prone to
problems in ms-access. A developer in VB6, c++, or in ms-access would
normally create a view on the server side, or use a pass-through query. So,
all I am saying that good developer practices that make sql server work well
applies to c++, VB, and ms-access developers. The POINT I AM MAKING here is
that it is NOT ms-access is the problem for performance with sql server as
is
WIDELY stated. Sure, joins via linked tables is a problem..but then again,
users of other development environments DO NOT have this option anyway!!
This
issue here is of POOR practices...NOT ms-access!
>
> I know that the use of linked views will provide some relief about the
> lack of speed of linked ODBC tables; however, I don't see why this could
> be considered as an advantage:
>
> 1) It will take as much time creating all the necessary views for each
> form
Why do you need to create a view for each form? I am not suggesting that at
all!!!! If you got a form bond to a table, and in my many years of ms-access
development, MOST FORMS are bound to ONE TABLE, then you don't have a
problem!.
Ms-access via odbc tables (no joins...right!), just works fine. In fact, you
get every bit the performance of a adp in this case!!
Sure, in this posers example, a continues form with complex join was
obviously
going to involve SEVERAL tables, and thus one needs to use a view. Again,
a person with a brain will simply make a decision here as to the best
approach
(you got complex joins...use a view...you got a single table..then using the
link to the table is fine!). However, no where do I suggest that you replace
a form bound to a linked table with a view ALL THE TIME.
I also should point out that a form/sub form works well with
linked tables.
>
> 2) When I will really need to use a stored procedure - for example for
> having access to temporary tables, cursor, other stored procedures, etc. -
> because of the underlying complexity of the request, I will have a pretty
> leg if I've limited myself to the exclusive use of views because I'm using
> ODBC linked tables.
Well, which do you need? If you need to use a stored proc, then do so!! My
gosh, do I need to get you some diapers here? I am stunned here? If you need
a stored proc, and want to pass some parameters to it, then used a stored
proc? What are earth is the problem here? You sure as the heck don't need a
store proc in place of sql view???? (I am complete missing the point
here???). Are you actually hinting to use stored procs in place of views?
Look, all I am saying here is that a store proc that returns some values
from a table has ZERO advantage over a view.
Further, what is stopping you/anyone from using stored procs here? Heck,
use ADO....it been included in the default references for the last 3
versions of ms-access. Use ado to create, and "execute" your stored procs.
It is certainly a great thing to do, and I not sure exactly where I am, or
(am not) suggestion to do such thing???????
> I don't see why limiting myself to the exclusive use of views and
> forgetting about stored procedures will make me a better programmer but I
> you want to go on this path, this is your right and your decision; not
> mine.
Gee, where did I suggest that? I most certainly did suggest that using a
store proc has zero advantages over a view to return values.
<my quote>
HUH? You mean grabbing data from a link view vs a stored proc makes any
difference here? (it makes not ONE bit!!).
</quote>
So, in fact I am CLEARLY pointing out that you don't just use a store proc
if
you don't need to!! (again, what more would one say!!!). I am saying that is
a store proc don't give you an advantage, then you don't need to use one!!
(again, how simple do we want this discussion to get!!).
Of course, if you need a store proc, or that stored proc give you an
advantage..then use it!! If I have a table with 100 names it in, and I need
to return those 100 names, how on earth does using a store proc over a view
get me those 100 names any faster? How does the store proc reduce
bandwidth?
Hence, now, you come up with this gem:
<quote>
> The use of linked views will greatly reduce the performance hit but even
> with them, I don't see the benefice of creating hundred of views instead
> of creating hundred of stored procedures.
</quote>
No, nor does making 100 store proc give you an advantage (so, then, what
exactly what YOUR point!!). MY WHOLE POINT HERE IS NEITHER gives an
advantage. So, now why are you stewing big deal about store proc then? I
stated NOTHING on this issue either way. Apparently, you seem to have big
issue here!!
As I mentioned, if a stored proc is an advantage..then use one!! (I am just
shaking my head here..trying to figure out what the problem here is!!).
I make NO claim, or NO suggestion here to NOT use store procs.
I am certainly sorry that you seem to misunderstand me. And, perhaps it is
my fault that was miss-understood.
I am very sorry if I came across the wrong way here on this issue.
It was not in any way my intention to suggest that one should not use store
procs, and even more so I did not intend to suggest that one should use a
view over a stored procs when one SHOULD use a stored proc!
however, the myth of ms-access not scaling well with sql server, or the fact
of a odbc connection to sql server no working well is a false one, and it is
NOT the fault of ms-access. The only blame here in terms of bad performance
is that of developer practices.
Albert D. Kallal
> what are being used here; yet you offer them as a solution.
>
> From my original post:
>
> "I have a situation with an ODBC linked view in an Access 2000 MDB...."
Ok, that is a surprise!
(and, you are right!!..I did miss the fact that you got a linked view!!).
Are you using filters on the form? (don't..if you are!!). Use the "where"
clause, and you can even stuff directly into he continues form the sql of
the view with parameters..and it should perform very good.
Hence, you can even go:
me.RecordSouce = "select * from MyView where city = 'Edmonton'"
So, does your continuous form have any type of filtering? If the form does
not, and in both cases, the ADP, and the odbc are just data being returned
from the view, then I would have to think that he data set being returned is
very large. It is certainly possible in this case that the ADP does a better
job of "displaying" the data. Then again, I would reduce the number of
records being returned to the form. There might be some different
interaction going on here..but you are using the same network..and the data
transfer in both cases should be the same....
I find my continues forms connected via ODBC to sql server display instant
in my cases. and, in fact you can even have the luxury of stuffing the sql
into the continues form as I did above..and again with odbc..the view works
very well indeed....
Albert Marshall
>
>Are you using filters on the form? (don't..if you are!!). Use the "where"
>clause, and you can even stuff directly into he continues form the sql of
>the view with parameters..and it should perform very good.
>
table that has had a filter saved on it. Open the view in Access in
design view and open the table properties. Look for anything in the
Filter line.
Failing that ,just open the view in datasheet view and right-click in
any field. Select 'Remove Filter/Sort', save the table and close it.
--
Albert Marshall
Marshall Le Botmel Ltd
01242 222017
Neil
While I'm not using filters on the form, this issue of the linked view
dragging in MDB but being zippy in the ADP occurs when the view is opened by
itself in the database window, without any form.
> So, does your continuous form have any type of filtering? If the form does
> not, and in both cases, the ADP, and the odbc are just data being returned
> from the view, then I would have to think that he data set being returned
> is very large.
As noted in my other post to you (posted after this one), the view only
returns 1154 records -- very small -- and has 24 fields.
> It is certainly possible in this case that the ADP does a better job of
> "displaying" the data. Then again, I would reduce the number of records
> being returned to the form. There might be some different interaction
> going on here..but you are using the same network..and the data transfer
> in both cases should be the same....
This happens even without a network -- using the database on my laptop with
MSDE I get the same results of MDB vs. ADP.
> I find my continues forms connected via ODBC to sql server display instant
> in my cases. and, in fact you can even have the luxury of stuffing the sql
> into the continues form as I did above..and again with odbc..the view
> works very well indeed....
Well, like I said, I don't know what the hangup is; all I know is what I
see -- the ADP displays and scrolls instantly, and the MDB with linked view
has a serious delay in scrolling. So something's going on here.
Neil
Neil
"Albert Marshall" <albert....@stowdata.co.uk> wrote in message
news:4aqYVCGp...@stowdata.demon.co.uk...
Sylvain Lafontaine fill the blanks, no spam please
Access. I will stop before your heart got an attack.
S. L.
"Albert D. Kallal" <kal...@msn.com> wrote in message
news:NbE%d.750174$6l.318096@pd7tw2no...
jimfo...@compumarc.com
> answers: Yes, ADP will be faster if you don't pay attention to
avoiding
> bottle necks, and thinking about what is going on....
I have some questions related to thinking about what is going on.
I found your discussion here particularly illuminating:
http://groups-beta.google.com/group/comp.databases.ms-access/msg/192953d273484b28
Are there other ways of thinking about ADP and MDB that would similarly
clarify things?
Based on [SQL Server 7.0 info]:
http://www.microsoft.com/technet/prodtechnol/sql/70/books/c0618260.mspx
Did the idea of indexed fields causing a particular "page" to load come
from leveraging assembly language concepts?
The page split mechanism seems to imply a natural 4K memory row
limitation (i.e., 8K / 2). What is the real row memory limit in
Access? I think Trevor discussed this once somewhere in
comp.databases.ms-access. Was the way memo fields are handled by
Access influenced by the page split mechanism? E.g., must row records
be kept under 4K so that the entire row's data will fit on the data
page during a page split?
The comparison of Access' pages with memory segments made me think of
the bizarre idea of installing Access on a RAM disk. Has anyone ever
tried something like that?
I've tried not to get too far into how Access is designed but a little
more knowledge will put some sense behind some of Access' limitation
tradeoffs and help me compare design alternatives.
Disclaimer: I don't usually think this way until late at night.
James A. Fortune
Neil
Can you give me some examples of the kind of workarounds you have to do to
get the ADP to work at all? I find this situation with the MDB dragging with
a straight attached view but the ADP zipping along very discouraging, and
I'm reconsidering using an MDB instead of an ADP. So I probably need a good
dose of ADP problem anecdotes to keep me on the MDB straight and narrow. :-)
Thanks,
Neil
"Steve Jorgensen" <nos...@nospam.nospam> wrote in message
news:vvgr31l3buv11blqb...@4ax.com...
> On Sun, 20 Mar 2005 12:32:10 -0500, "Sylvain Lafontaine" <sylvain aei ca
> (fill
> the blanks, no spam please)> wrote:
>
>>You may try to add a virtual index on your linked view:
>>http://support.microsoft.com/kb/q209123/
>>
>>If this doesn't help, then you will have to use an unbound form coupled
>>with
>>SQL pass-through queries (or ADO objects) to resolve your speed problem
>>with
>>MDB. Another solution could be to go with TS to simulate a high-speed
>>LAN.
>>
>>I don't know where you got the impression that MDB were about the same as
>>ADP in term of speed. It has been repeated a number of times that the use
>>of MDB' linked tables and views is only a workable solution for small
>>databases on a fast Lan.
>
Neil
situation.
First, note that the view in question had one main table, two lookup tables,
and a subview. Again, when linked to the MDB file it would scroll very
slowly; but in the ADP file, it was zippidy fast.
I took out the two lookup tables, and reattached the view, and it became
fast in the MDB file as well. However, when I took out just one lookup table
and reattached the view, it was still slow.
Looking for some sort of setting that might help, I stumbled up Encrypt
View. I made a copy of the original view (with both lookup tables) and
encrypted it, and it became zippidy fast in the MDB file!
Great, I figured; now I have to encrypt all my views that are slow and keep
a spare copy for editing. However (and this is the really bizarre part) that
turned out to not be the case.
Though I had tried refreshing the original link before encrypting the view
copy (with no improvement), I tried refreshing the link again after
encrypting the view copy, and, it too was zippidy fast.
In other words, though the original view was unchanged, after I made a copy
of it and encrypted that copy, it became fast again.
I don't understand what happened here, but it clearly must be some sort of
compile/optimization issue which kicked in when I encrypted that copy of the
view.
So if anyone has any idea as to what's going on here, it would be
appreciated. Also, is there any way to force whatever happened here to
happen without having to make a copy of a view, encrypt it, and then delete
it?
Thanks everyone for your assistance.
Neil
Joe Fallon
FWIW, I stopped using Refresh link years ago.
Now I just drop all links and re-create from scratch.
The optimization you noted is one of the many benefits of this approach.
I have posted my re-linking code about a billion times in the last 7 years.
But if you want to see it, let me know.
--
Joe Fallon
Access MVP
"Neil" <njo...@pxdy.com> wrote in message
news:8KL%d.757$gI5...@newsread1.news.pas.earthlink.net...
Sylvain Lafontaine fill the blanks, no spam please
valid): make that the names of the indexes of all primary keys come first in
alphabetical order before any other indexes. The old trick was to add a lot
of letter a at the beginning, something like: aaaaaPK_MyTable_MyField.
Access 97 was using the alphabetical order to determine which index was the
primary key. Don't know if it's still valid for A2000+.
S. L.
"Neil" <njo...@pxdy.com> wrote in message
news:8KL%d.757$gI5...@newsread1.news.pas.earthlink.net...
Sylvain Lafontaine fill the blanks, no spam please
the issue here.
S. L.
"Neil" <njo...@pxdy.com> wrote in message
news:8KL%d.757$gI5...@newsread1.news.pas.earthlink.net...
Neil
of the view, trying different things, I would attach the new view from
scratch into the database. Still was sluggish. Only after I encrypted that
one view did things change. Strange.
Neil
"Joe Fallon" <jfal...@nospamtwcny.rr.com> wrote in message
news:eL4gb$oLFHA...@TK2MSFTNGP12.phx.gbl...
Neil
have to worry about what other indexes are named. I don't like having to
remember to name an index such and such to avoid a data problem. I prefer to
rename the PK, and then it's set whether I remember when creating other
indexes or not.
Neil
"Trevor Best" <nos...@besty.org.uk> wrote in message
news:423fd065$0$32602$db0f...@news.zen.co.uk...
> Sylvain Lafontaine wrote:
>> Here a suggestion from the past (Access 97, doesn't know if it's still
>> valid): make that the names of the indexes of all primary keys come first
>> in alphabetical order before any other indexes. The old trick was to add
>> a lot of letter a at the beginning, something like:
>> aaaaaPK_MyTable_MyField.
>>
>> Access 97 was using the alphabetical order to determine which index was
>> the primary key. Don't know if it's still valid for A2000+.
>
> Yes it is. I generally design tables in SQL Server and it gives the name
> PK_whatever to the primary key, however now when I create an additional
> unique index I give it the name uidx_whatever.
Trevor Best
> Here a suggestion from the past (Access 97, doesn't know if it's still
> valid): make that the names of the indexes of all primary keys come first in
> alphabetical order before any other indexes. The old trick was to add a lot
> of letter a at the beginning, something like: aaaaaPK_MyTable_MyField.
>
> Access 97 was using the alphabetical order to determine which index was the
> primary key. Don't know if it's still valid for A2000+.
Yes it is. I generally design tables in SQL Server and it gives the name
Neil
encrypting the view copy *did* in fact increase performance, there was a
price to pay. Apparently, when I encrypted the view copy and then refreshed
the original view's link, the original view's link lost its virtual primary
key. (Don't know why, but that's what happened. And I was able to reproduce
this phenomenon.) And, apparently, not having the virtual primary key made
the linked view scroll faster.
To test this I created two links to the same view: one with, and one without
virtual primary key. The one without the virtual primary key scrolled fast,
just like the ADP file; the one with the virtual primary key was slow.
I ran a trace on these two and on the ADP file when opening and scrolling
the view, and I think I see what's going on here.
When opening the view in the ADP file, profiler shows the following:
SELECT * FROM "vwWebMaintDuplicates"
However, when opening the linked view with the virtual primary key in place
from the MDB file, I get the following:
SELECT "dbo"."vwWebMaintDuplicates"."Index" FROM
"dbo"."vwWebMaintDuplicates"
sp_prepare @P1 output, N'@P1 int,@P2 int,@P3 int,@P4 int,@P5 int,@P6 int,@P7
int,@P8 int,@P9 int,@P10 int', N'SELECT
"Index","TITLE","AUTHILL1","attFirstEdition","attSigned","SignedCond","YRPUB","PRICE","Web","Status","WebStatusPending","ActivateDate","DeactivateDate","WebAddedBatchID","AllowDuplicate","WebAction","WebActionPending","DateModified","DateWebActionApplied","JIT","MImage","HImage","AdCode","OnWeb"
FROM "dbo"."vwWebMaintDuplicates" WHERE "Index" = @P1 OR "Index" = @P2 OR
"Index" = @P3 OR "Index" = @P4 OR "Index" = @P5 OR "Index" = @P6 OR "Index"
= @P7 OR "Index" = @P8 OR "Index" = @P9 OR "Index" = @P10', 1 select @P1
sp_execute 4, 1364, 1971, 1978, 2303, 3140, 3480, 3605, 4962, 6747, 6749
SELECT
Index","TITLE","AUTHILL1","attFirstEdition","attSigned","SignedCond","YRPUB","PRICE","Web","Status","WebStatusPending","ActivateDate","DeactivateDate","WebAddedBatchID","AllowDuplicate","WebAction","WebActionPending","DateModified","DateWebActionApplied","JIT","MImage","HImage","AdCode","OnWeb"
FROM "dbo"."vwWebMaintDuplicates" WHERE "Index" = @P1 OR "Index" = @P2 OR
"Index" = @P3 OR "Index" = @P4 OR "Index" = @P5 OR "Index" = @P6 OR "Index"
= @P7 OR "Index" = @P8 OR "Index" = @P9 OR "Index" = @P10
"Index" is the name of the primary key field in the main table in the view,
and it's the field that's used as the virtual primary key. The numbers 1364,
1971, etc., above, are the Index values for the first records that are
returned.
Thus, the MDB linked view with virtual primary key first gets a list of pk
values, then grabs the records ten at a time, specifying the pk values to
get.
This would explain why it's slow in scrolling -- it only gets the records in
sets of ten and has to keep grabbing them.
When I open the linked view in the MDB without the virtual primary key,
profiler shows:
SELECT "Index" ,"TITLE" ,"AUTHILL1" ,"attFirstEdition" ,"attSigned"
,"SignedCond" ,"YRPUB" ,"PRICE" ,"Web" ,"Status" ,"WebStatusPending"
,"ActivateDate" ,"DeactivateDate" ,"WebAddedBatchID" ,"AllowDuplicate"
,"WebAction" ,"WebActionPending" ,"DateModified" ,"DateWebActionApplied"
,"JIT" ,"MImage" ,"HImage" ,"AdCode" ,"OnWeb" FROM
"dbo"."vwWebMaintDuplicates"
This is essentially the same as what's going on in the ADP file, except that
it's specifying a field list, instead of "*".
Thus, without the virtual primary key, the MDB link is fast, like the ADP
file, because it's just getting a set of records. With the virtual primary
key, though, it's getting the list of pk's, and then grabbing records ten at
a time.
This appears to be an inherent property of the way the MDB file/ODBC driver
handles virtual primary keys, and doesn't appear to be anything I can
change. So the question still remains: why is it going slowly when it used
to not, and what can I do about it? Is there anyway to tell it to get all of
it's "sets of ten" at once, when the view is opened, rather than waiting
until the view is scrolled? Are there any other workarounds or settings that
can be tried here?
Anyway, we seem to be back at square one. But at least there's a bit more
knowledge now, and at least it explains the performance increase when the
encryption took place (though not why the virtual pk was lost in the first
place).
Thanks!
Neil
"Neil" <njo...@pxdy.com> wrote in message
news:8KL%d.757$gI5...@newsread1.news.pas.earthlink.net...
Neil
> As a last try, you might want to take the ONE form, and the ONE link and
> put
> it into
> another mdb file..and test it separately outside of the existing
> application...
This was a good idea. I tried it. Same results.
Neil
Albert D. Kallal
Hum...1100 records is not much...
I have to think that some "thing" is not 100% here.
>
> This happens even without a network -- using the database on my laptop
> with MSDE I get the same results of MDB vs. ADP.
Excellent observations again...and the fact that you point out this occurs
when opening the linked "view" directly without a form is also very
helpfull.
At this point, I think we have some performance problem here...and one that
is
the result of some feature that needs to be turned off...
I would first try deleting the link to this view..and then re-create it....
Perhaps there is some lookup, or something that is grabbing data from MORE
then one data source..as that would cause a problem here. Also, you should
not have ANY links that are dead...or non existing..as I seen that as a
problem
also.
As a last try, you might want to take the ONE form, and the ONE link and put
it into
another mdb file..and test it separately outside of the existing
application...
But, at this point...I am at a loss...
Neil
an index a certain prefix is one less thing to have to remember if I rename
the PK. But everyone has their preferences.
"Trevor Best" <nos...@besty.org.uk> wrote in message
news:424067ab$0$32611$db0f...@news.zen.co.uk...
> Neil wrote:
>> I usually just rename the PK to "aaaaaa...." or "__......" -- then you
>> don't have to worry about what other indexes are named. I don't like
>> having to remember to name an index such and such to avoid a data
>> problem. I prefer to rename the PK, and then it's set whether I remember
>> when creating other indexes or not.
>
> Well, as I said, I do in SQL Server, I have to name the index, it doesn't
> spoil me the way Access does :-)
Trevor Best
> I usually just rename the PK to "aaaaaa...." or "__......" -- then you don't
> have to worry about what other indexes are named. I don't like having to
> remember to name an index such and such to avoid a data problem. I prefer to
> rename the PK, and then it's set whether I remember when creating other
> indexes or not.
Well, as I said, I do in SQL Server, I have to name the index, it
doesn't spoil me the way Access does :-)
--
Bri
You said it was fast before you added the last three fields? Why don't
you remove those fields again, verify that it is indeed still speedy
with the virtual PK in place and see what the profiler says its doing then.
Perhaps there is something about these three fields that is triggering a
change in the execution plan. I know in Access itself (ie an Access BE)
that there are queries that Access will only grab the first so many
records and then continue to get more in the background as you scroll
through. IIRC, there may even be documentation on what triggers this.
Leaving the view without the virtual PK is not an option if you need
to be able to edit this view.
Oh, another thought, try changing the PK field name in the view to
another name. 'Index' might be a reserved word and that might add
overhead/confusion while it resolves that (I know it can figure it out,
but why make it do it if it doesn't need to).
Good and persistant work in tracking things down so far. This is a
strange one.
--
Bri
Trevor Best
> Leaving the view without the virtual PK is not an option if you need to
> be able to edit this view.
Not necessarily, since the view contains more than 1 base table I doubt
that SQL Server will allow an update to it without use of an "instead
of" trigger.
Neil
"Bri" <n...@here.com> wrote in message
news:1Eg0e.761680$Xk.358633@pd7tw3no...
> Neil,
>
> You said it was fast before you added the last three fields? Why don't you
> remove those fields again, verify that it is indeed still speedy with the
> virtual PK in place and see what the profiler says its doing then.
I tried that before, and it seems the same without those three fields. So
either I was imagining that it was faster, or something else is going on.
> Oh, another thought, try changing the PK field name in the view to another
> name. 'Index' might be a reserved word and that might add
> overhead/confusion while it resolves that (I know it can figure it out,
> but why make it do it if it doesn't need to).
The name that Access (automatically) gave the vpk is "__uniqueindex" with
"Index" as its only field.
>
> Good and persistant work in tracking things down so far. This is a strange
> one.
Indeed. Raises the question: why am I staying with the MDB? Oh, right,
because others said that ADPs are much more problematic, even if better in
some ways.
Neil
Neil
"Trevor Best" <nos...@besty.org.uk> wrote in message
news:4241c8fd$0$32603$db0f...@news.zen.co.uk...
Larry Linson
> Indeed. Raises the question: why am I
> staying with the MDB? Oh, right,
> because others said that ADPs are much
> more problematic, even if better in
> some ways.
There's an old adage in the computer business: if it doesn't work, it
doesn't matter how fast it is. I think it is a telling point that a number
of respected, early adopters, advocates of ADPs have now abandoned their
use.
That said, in the very modest amount of modification/update work that I have
done with ADPs, I did not encounter any instances in which they just did not
work. Perhaps some of what appeared to be rather unusual design features
were, in fact, workarounds that the original author had to employ. However,
I suspect that most were because he did not realize that the SQL Server
tables had to have a Primary Key to be updateable when used with bound
Forms.
Larry Linson
Microsoft Access MVP
Albert D. Kallal
> http://www.microsoft.com/technet/prodtechnol/sql/70/books/c0618260.mspx
>
> Did the idea of indexed fields causing a particular "page" to load come
> from leveraging assembly language concepts?
No, the concepts of "code" page in terms of assembler, is NOT related to the
above concept in a database. A "code" page in assembly is often just a
reference to a frame of data (in memory) used for some type of "mapping".
Often this type of mapping is referring to Localization (different languages
in windows for example have a code page, one is different for French,
English etc. You "load", or set a pointer to that page..and thus all
routines now transfer different characters etc correctly).).
> The page split mechanism seems to imply a natural 4K memory row
> limitation (i.e., 8K / 2). What is the real row memory limit in
> Access?
I am not sure what the page size used, but I do believe it is 4k. As
computers get faster, and more ram available, the page size tends to go up a
bit. (too large, and you do waste disk i/o).
Remember, access97 (JET 3.x used page locking, and did not support record
locking). JET 4.0 (access 2000 and later) does in fact support record
locking. (what actually happens is the page lock occurs only during a
update...as each record can now be locked individual).
Remember, since records in ms-access now are VARIABLE length, then you need
a means to resolve to SINGLE record. What happens is the index routines
eventually translate WHERE/what BUCKET the record you are looking for. At
this point, when the bucket if found..then a SEQUENTIAL SEARCH occurs for
your record!!. Thus, with small records, you might easily fit 10 records
into a page (note that I am using the word, page, frame, bucket interchange
here...they all mean the same thing!).
This page based systems also explain why often running some update routines
can cause serous file bloat. IF the group of records you just modified now
expands beyond the size of the bucket where the records reside..then you got
split up the page..and re-arrange the records. If you go over the page size
by just ONE byte, you need a WHOLE NEW page, and the all of the "rest" of
the page is wasted. Of course, now that you got a extra almost empty
page..some records can be added without having to expand the file. (this is
why a file grows REAL fast RIGHT after a compact (any adding will cause
spillage out of the tightly packed frame. As the application use settles
down, then each time you modify a record, it is more likely to fit in its
page..and not spill over into another "needed" page).
So, note that each of those page frames are OFTEN referred to as a bucket in
database systems. And, normally, a hash-code scheme is used to resolve the
location of a stored record to that single bucket....then at which time a
sequential search occurs. These buckets are thus the SMALLEST size of data
that the JET engine can work with.
> Was the way memo fields are handled by
> Access influenced by the page split mechanism? E.g., must row records
> be kept under 4K so that the entire row's data will fit on the data
> page during a page split?
I don't know the answer to the above. However, memo fields can be quite
large in size...and thus really are just a "list" of linked frames. The
limit of the size of a memo field is thus just a question of how many bytes
in the linked list of frames is allowed. For example, if you only allow 1
byte, then you can have from 0 to 255 frames linked sequentially. I also
don't know if the frames have a forward link + backward link (some systems
do). Anyway, lets just assume a forward link byte in each frame. Thus, you
can have 0-255 linked frames x 4k would be your max object size....which is
of course not the case here. In fact, a memo field can be 1 gig in size.
(so, the link list data must be about 32 bits in size..as 16 would not be
enough). So, a large memo is just a sequential list of frames linked
together.
>
> The comparison of Access' pages with memory segments made me think of
> the bizarre idea of installing Access on a RAM disk. Has anyone ever
> tried something like that?
While the data in the disk file is organized in "pages", or so called
frames, the fact is that the operating system (windows) takes parts of the
file that JET is working on, and pulls it into ram anyway. Further, JET
maintains it own cache in ram of "frames". So, after you update, or read a
few records, then they are in ram anyway. In fact, JET can mark a frame for
update..but wait..and do something more important (like read a frame in the
pending list of frames to be read).
You certainly would see some performance improvements by placing a database
in a ram based drive, but those performance improves would be UN-related to
the fact of JET being a "frame", or page based database system.
And, for files of only a few megs, and smaller table sizes, the whole table
gets well cached in memory anyway..
Neil
> have
> done with ADPs, I did not encounter any instances in which they just did
> not
> work. Perhaps some of what appeared to be rather unusual design features
> were, in fact, workarounds that the original author had to employ.
> However,
> I suspect that most were because he did not realize that the SQL Server
> tables had to have a Primary Key to be updateable when used with bound
> Forms.
Not sure I'm following you here. You mean the original author of the ODBC
mechanism for getting SQL records? Sorry for not following.
Neil
Larry Linson
> Not sure I'm following you here. You mean
> the original author of the ODBC
> mechanism for getting SQL records?
No, I am sorry that I was not clear -- I meant the author of the application
database I had to modify. Although ADP/ADO seemed a bit "quirky" to me, and
not as straightforward as DAO, it did work properly in the areas I had to
modify.
The client was primarily interested in features and function (and
controlling costs), so there was no opportunity to compare ADP/ADO versus
MDB/DAO.
In the one instance where a colleague did address a performance issue, it
was a "communication issue", not an Access issue.
david epsom dot com dot au
If you open your linked view in the database window.
you will see the row pointer, and, eventually, the total
number of records, updated continuously as Access gets
the records.
If this is causing problems, you might be interested
in playing around with different methods of accessing
the linked view.
For a start, try using an ADO or DAO object instead
of the Access Application object (clicking in the
database window is equivalent to application.DoCmd
or application.OpenQuery)
"Set rs = application.codedb.openrecordset" won't
give you a visible data sheet, but it should run faster,
and you have a number of options for what kind of
recordset you want. Obviously, it won't solve your
problem, but it might be interesting.
Another thing you can try is 'record level locking'.
Turn that off if you can: I've noticed an obscure effect
on ODBC transaction handling, which indicates that
the connection is subtly different when this option
is selected.
Regarding ADP vs MDB: it is only fair to note that those
people who advocate MDB over ADB would not in general
countenance the opening of a view in datasheet view
at all. Accepted wisdom is that, as when using a bank
ATM, the user should request only one record, and only
the requested record should be displayed.
BTW, a classic cause of the kind of behaviour you are
seeing is ---- inadvertent SQL or ODBC logging ----
Check that you haven't accidentally left logging turned
on somewhere :~(. The Jet settings are TraceSQLMode
and TraceODBCAPI: there are more places to turn on
tracing in your ODBC DSN etc.
(david)
"Neil" <njo...@pxdy.com> wrote in message
news:Mt30e.2142$H06...@newsread3.news.pas.earthlink.net...
jimfo...@compumarc.com
> ...
Thanks for your insights. I used to think that each record was
indexed. I'll keep Access' scheme in the back of my mind. Hmm.. what
if I had a text field called 'Bank' filled with junk text? When
getting ready to add other data via code I could 'go to the Bank' and
throw away some junk. Would that prevent page splits from happening?
Just before compacting the db I could refill the Bank to make room for
more new data. BTW, I'm not seriously considering this idea.
James A. Fortune
Neil
> you will see the row pointer, and, eventually, the total
> number of records, updated continuously as Access gets
> the records.
In this case, though, we're dealing with a very small number of records
(usually < 200). When the form is opened, the total number of records
appears immediately, indicating that all records have been brought in. Yet
the form is hideously slow in scrolling. Even displaying the initial screen
of about 20 takes forever (about 5 seconds :-) ).
All this could be attributed to the MDB blues. However, as noted, this form
has been in place for a long time without any slowness. All of a sudden, it
started acting this way, and I can't track it down.
> For a start, try using an ADO or DAO object instead
> of the Access Application object (clicking in the
> database window is equivalent to application.DoCmd
> or application.OpenQuery)
Not sure what you mean by "clicking in the database window." In my case, the
form is opened or the user specifies an option in the form and the recordset
is reset. A dynamic SQL statement is built, and the form's recordsource is
set to the SQL.
I did try opening a DAO recordset and setting the form's Recordset property
instead of using the Recordsource, but the results were the same.
> Another thing you can try is 'record level locking'.
> Turn that off if you can: I've noticed an obscure effect
> on ODBC transaction handling, which indicates that
> the connection is subtly different when this option
> is selected.
All locking in the form is off.
>
> Regarding ADP vs MDB: it is only fair to note that those
> people who advocate MDB over ADB would not in general
> countenance the opening of a view in datasheet view
> at all. Accepted wisdom is that, as when using a bank
> ATM, the user should request only one record, and only
> the requested record should be displayed.
Well, that would be simpler, of course. But there are times when you need
continuous form view. And, as noted, it's been working fine until recently.
BTW, since you mention those who advocate MDB over ADP, does that mean that
you're an advocate of ADP?
> BTW, a classic cause of the kind of behaviour you are
> seeing is ---- inadvertent SQL or ODBC logging ----
> Check that you haven't accidentally left logging turned
> on somewhere :~(. The Jet settings are TraceSQLMode
> and TraceODBCAPI: there are more places to turn on
> tracing in your ODBC DSN etc.
I haven't seen any places to turn this on on an application level. And since
this is happening globally (both on the client's LAN, as well as on my local
PC), I can't see all of the machines having that turned on. Or is there a
global setting for the application itself, rather than the PC?
Thanks,
Neil
david epsom dot com dot au
> (usually < 200). When the form is opened, the total number of records
> form is hideously slow in scrolling. Even displaying the initial of about
I suggest that you start a new thread with this information.
Don't mention ADP's at all. Do mention that it is SQL Server,
and that it works differently if there is no primary key defined.
'--
I'm not an advocate on the mdb/adp issue: I just don't
use adp. We have a very large application with most
customers using an MDB backend: we do the best we can
for SQL Server clients.
Record-Level locking is a Engine-level option,
controlled by Access when a database is opened:
Tools | Options | Advanced
You have obviously loaded a 'dyanaset' instead of a
'snapshot': Jet has retrieved pointers to all of the
records, and is now laboriously retrieving the data,
10 records at a time. The switch may have happened
just because of the size of the records increased.
'---
(david)
"Neil" <njo...@pxdy.com> wrote in message
news:bhu4e.1036$An2...@newsread2.news.pas.earthlink.net...
Neil
> controlled by Access when a database is opened:
> Tools | Options | Advanced
My understanding is that the option in Tools | Options | Advanced is only
the default record locking for forms, reports, and queries. That is, when a
new object is created, it is given the default record locking option
specified there.
I suppose if one edits data directly in a table, the default record locking
option comes into play. But when there is a form, report, or query, the
RecordLocks property of that object trumps the default record locking option
specified in Tools | Options | Advanced. That's my understanding, anyway.
Regardless, the point is somewhat moot, since, when dealing with a SQL
database, Jet can't lock the records anyway. From Access online help:
"Note When you edit data in a linked SQL database table by using ODBC,
Microsoft Access doesn't lock records; instead, the rules of that SQL
database govern locking. In this instance, regardless of the record-locking
setting you choose for your database, Microsoft Access always acts as though
the No Locks setting has been selected."
>
> You have obviously loaded a 'dyanaset' instead of a
> 'snapshot': Jet has retrieved pointers to all of the
> records, and is now laboriously retrieving the data,
> 10 records at a time. The switch may have happened
> just because of the size of the records increased.
That could be; but one wouldn't think that going from 21 fields displayed to
24 would make that much of a difference. Also, I tried removing the three
fields, and it's still slow -- which leads me to wonder if it's some sort of
optimization issue on the SQL end which will eventually work itself out.
Probably not; but it's a thought.
Neil
david epsom dot com dot au
locking" controls the way databases are opened. The options
are record-level locking and page-level locking. Another
'kind' of locking is table-level locking. At the engine level,
these are the kinds of locks that are used.
The decisions about WHEN to lock (early, late, never,
optimistically, pessimistically etc) are controlled
separately, for example by form properties.
Theoretically, there is no reason why the lock scope should
affect the data transfer strategy, but I have noticed some
odd effects of this setting, which is why I suggested that
you try changing it.
(david)
"Neil" <njo...@pxdy.com> wrote in message
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Neil
handled on a per-machine basis, and this is something that changed in the
database (either SQL back end or front end MDB), since it happened across
the board, both locally and across the LAN.
N
"david epsom dot com dot au" <david@epsomdotcomdotau> wrote in message
news:OFQvvDwO...@TK2MSFTNGP09.phx.gbl...
Alex - IntraLAN
great post, good debate, I just want to add my opinion to the post. I
have been using access for years since Access v2, I have used all
combinations of front-end/back-end technologies and the conclusion I
have drawn is this. If you want a database of < 100mb in size the MDB
method works very well, as soon as you are in a large database > 200mb
100+ tables 100+ forms then adp style projects seem to be better as the
maximum underlying connections to a DB is 2048 and linked MDB/ODBC
tables require 2 connections for every table/combo box/and other table
style connections and ADP/SQL tables only require 1. I have only hit
this limitation 3 times in my 10+ years developing access applications,
but when I hit it with the MDB I have only one choice convert to an ADP
project. From a performance perspective I would say that DAO is
slightly faster using similar code/loops etc to ADO, but once the move
to ADP has been made then it is a shame if the application is not
optimised using stored procedures to run the main code loops that don't
require user input or progress to the screen whilst running, I see
performance increases of 10x+ using stored procedure over client side
code loops. At the end of the day it is horses for courses, small apps
+ small data MDB every time, big app + big data ADP/SQL every time. I
keep hearing of problems with ADP projects I have not had any major
problems with these and I have one site running an ADP (access
2000)/SQL7 application on 150+ terminals I have not had to fix or get
involved in anything for 4 years. The most important thing to me is db
design with as much of the program logic held in the database and not
the front end. A couple of thing that I have done to improve query
performance is
never use 'Select * from' and to trim the field length of long fields
if the results are going to a list box 'SELECT
Convert(char(30),rsContacts.Name_Of_Solicitor)' and to add the
following to the end of those line 'FOR BROWSE' which seems to help
with locking on the server.
Just my thoughts.
Alex
david epsom dot com dot au
I don't think that the MDB subject is exhausted, but I
don't want to continue posting in an ADP thread if you
have start a newer, more relevant thread.
(david)
"Neil" <njo...@pxdy.com> wrote in message
news:1Z_4e.1943$An2...@newsread2.news.pas.earthlink.net...
Neil
Thank you for your very helpful post. A few comments below.
> the conclusion I
> have drawn is this. If you want a database of < 100mb in size the MDB
> method works very well, as soon as you are in a large database > 200mb
> 100+ tables 100+ forms then adp style projects seem to be better
The database file itself is about 200-270 mb; but it doesn't have that many
tables. There are two main tables, which make up most of the data; a few
medium-sized tables; and a slew of small lookup tables -- roughly 80 tables,
though I'd say that at any given time less than 10 are in use by any single
user.
> as the
> maximum underlying connections to a DB is 2048 and linked MDB/ODBC
> tables require 2 connections for every table/combo box/and other table
> style connections and ADP/SQL tables only require 1. I have only hit
> this limitation 3 times in my 10+ years developing access applications,
> but when I hit it with the MDB I have only one choice convert to an ADP
> project.
As noted, there aren't a lot of tables in use at any given time. And our
most complex form has maybe 40 combo boxes. So we don't seem to be
approaching this limit.
But, be that as it may, the situation I noted in this thread regarded a view
which was fast in an ADP file, and used to be just as fast in an MDB file;
but now is slow in the MDB file. This situation occurs:
* when I use the database files on my unnetworked PC running MSDE with no
other apps running;
* when the MDB file is open without any forms or reports open;
* when the linked view is opened by itself from the database window without
a form.
As noted previously, it takes about 5 seconds just to bring up a screen of
about 20 records, and each time the scroll bar is clicked (even when moving
down a single record), the same or a similar delay occurs.
This same view was working fine until recently, and was used for several
years as the recordsource for a form that edited it in Continuous Forms
view. I added a few fields to the view, and things slowed down. I tried
taking the fields out, but the results are the same. (The adding of the
three fields may have been coincidental to something else that may have
caused the slowdown.)
Either way, the view is still fast in an ADP file, but is slow as molasses
in its original MDB file.
> I
> keep hearing of problems with ADP projects I have not had any major
> problems with these and I have one site running an ADP (access
> 2000)/SQL7 application on 150+ terminals I have not had to fix or get
> involved in anything for 4 years.
That's good to know. One of the things I've been discussing here is that
this database is going to be rebuilt from the ground up (was converted to
Access from an old database program by a developer, then was modified by
another developer who didn't understand principles of normalized design,
then was inherited by me). I am leaning towards redoing it in MDB,
especially given the many testimonies of problems people have had with ADP.
But your input is certainly significant here as well. So that's good to
know.
> The most important thing to me is db
> design with as much of the program logic held in the database and not
> the front end.
Yeah, well, here the whole thing is in the back end. The whole idea is that
SQL Server does all the work and the MDB just has to get the data. But,
apparently, it has problems even with just that!
> A couple of thing that I have done to improve query
> performance is
> never use 'Select * from' and to trim the field length of long fields
> if the results are going to a list box 'SELECT
> Convert(char(30),rsContacts.Name_Of_Solicitor)' and to add the
> following to the end of those line 'FOR BROWSE' which seems to help
> with locking on the server.
I didn't see a "FOR BROWSE" option in the SQL 7 BOL. Is that a SQL 2000
option?
Thanks,
Neil
Neil
more, I'll go ahead and start a new thread. Will reply here again with the
name after I post it.
Thanks!
Neil
"david epsom dot com dot au" <david@epsomdotcomdotau> wrote in message
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