Trying to understand "multiple warm standby architecture" using MSA
bslade
15.x). It's titled "Using replicate databases as warm standby
databases", but I think they meant to say "Using replicate [MSA]
databases as warm standby [like] databases". In the body it says
it's an example of setting up "a multiple warm standby
architecture" (again [MSA] missing?)
Anyway, I can't figure out what this page is talking about. It talks
about warm standby setup, but there's no logical connection
information in any of the example text. And there's no example of a
"switch active" operation.
Is this really just continuous bidirectional data replication? (except
that DDL and system proc replication only works from dataserver A in
the example). If so, then the title is confusing/misleading since
this really isn't "warm standby" as defined in the Sybase world.
Especially since DDL isn't replicated in the MSA example once you
switch the primary (er "active") server.
Thanks in advance
Ben in Chevy Chase, MD
Luc Van der Veurst
"bslade" <Public...@benslade.com> wrote in message
news:d0b84d7b-6f41-45e7...@g1g2000vbr.googlegroups.com...
> I'm looking at Chap 12 in the Rep Server Admin Vol 1 manual (v 12.6 or
> 15.x). It's titled "Using replicate databases as warm standby
> databases", but I think they meant to say "Using replicate [MSA]
> databases as warm standby [like] databases". In the body it says
> it's an example of setting up "a multiple warm standby
> architecture" (again [MSA] missing?)
The online manuals (15.2 and 12.6) have "Chapter 12: Managing Replicated
Objects
Using Multi-Site Availability" as title, so it seems that it can't be
compared
to the document htat you have.
> Anyway, I can't figure out what this page is talking about. It talks
> about warm standby setup, but there's no logical connection
> information in any of the example text. And there's no example of a
> "switch active" operation.
There is a difference between "warm standby" as a concept and
the name of the implementation. When Sybase had only one implementation,
it was called "warm standby", then sybase added MSA wich can
also be used as a warm standby solution.
So when you see "warm standby" in the manuals, it can refer to the
concept or the implementation. Although the notion op "replicate
databases" is not part of the original warm standby solution and
leads implicitely to the MSA concept, I agree that it would be more
clear if Sybase explicitely mentions "MSA" whenever it talks about
the warm standby solution based on MSA.
> Is this really just continuous bidirectional data replication? (except
> that DDL and system proc replication only works from dataserver A in
> the example). If so, then the title is confusing/misleading since
> this really isn't "warm standby" as defined in the Sybase world.
> Especially since DDL isn't replicated in the MSA example once you
> switch the primary (er "active") server.
Bidirectional replication can be setup so that DDL is replicated.
Bidirectional replication as a warm standby solution means that
you only allow user connections to one site (the active site) while
the other site is not used, or only used for read only operations
(standby site).
With biddirectional replication as a warm standby soluition you have to
watch out if you do maintenance on the standby site that shouldn't
be replicated to the active site, but I think it's supperior to the
original warm standby implentation because when you have to
switch acitve and standby, the only thing to do is to make sure that
everone connects to the other site without having to cross your
fingers during switch active commands.
Luc.
bslade
Re: "Bidirectional replication can be setup so that DDL is replicated"
Did you mean "so that DDL is replicated *bidirectionally*" ? If so,
then why didn't sybase do that in their "Using replicate [MSA]
databases as warm standby [like] databases" manual page? Sybase
specifically says that DDL replication can only come from one database
in the MSA warm standby like config.
More specifically, in a bidirectional MSA replication setup, I'm
assuming that you don't get into looping update problems because of
the "alter connection to ReplicateServer.ReplicateDB set
dsi_replication ‘off’" command. But I'm wondering if DDL replication
is different and would loop if all the DB repdefs included the
"replicate DDL" option?
Ben
On Dec 2, 4:50 am, "Luc Van der Veurst" <dba_az...@hotmail.com> wrote:
> "bslade" <PublicMail...@benslade.com> wrote in message
Luc Van der Veurst
> Re: "Bidirectional replication can be setup so that DDL is replicated"
>
> Did you mean "so that DDL is replicated *bidirectionally*" ?
Yes.
DDL is replicated by configuring the rep agent and setting the
"send warm standby xacts" option to true.
Loops are avoided by altering the connection and
set dsi_replication_ddl 'on'.
The effect is that before sending a ddl command to the replicate database,
the repserver sends the "set replication off" command.
The maintenance user needs to have "set session authorization" granted.
It has been some months since I've been testing it, and other work
is keeping me from converting our warm-standby servers to a bi-directional
solution, but I remember I had one problem with the documentation
with regard to the dsi_replication_ddl and/or dsi_replication options.
Luc.
bslade
"dsi_replication" without the "ddl".
Also, did you mean set dsi_replication *off* ? As I understand it,
that should prevent replication loops.
Ben
Mark A. Parsons
bslade wrote:
> There is no dsi_replication_ddl option. I assume you meant
> "dsi_replication" without the "ddl".
RS 15.0 introduce a new configuration setting called dsi_replication_ddl.
See the 15.0 What's New manual as well as the 15.0 Reference manual for details.
The name and settings behaviour can be a bit confusing ... 'off' (default) means that DDL replication is enabled in the
replicate database ... 'on' means that DDL replication is disabled by issuing 'set replication off' <DDL-command> 'set
replication on' in the replicate database.
bslade
Since I'm using RS 12.6, I don't have access to this nifty new feature
yet. But with RS 12.6 I could setup MSA bidirectional data
replication, and then manually run "alter database replication
definition MyDbRepDef with primary at ServerName.MyDb [not] replicate
DDL" to turn off DDL replication from the one side, then turn on DDL
replication from the other side. In fact, I tested this and it
works! But upgrading to RS 15 would certainly make this cleaner.
Thanks very much for all the help.
Ben
On Dec 3, 3:22 pm, "Mark A. Parsons"