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Using ISHELL to change the mount mode on the shared plex root?

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Gregg Kimbrough

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Jul 20, 2010, 2:42:36 PM7/20/10
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Hiya:
anyone have any experience on changing a shared sysplex root using the
Ishell? Impacts: like TCPIP coming to an halt while it does the unmount and
remount behind the scenes? I'm trying to avoid doing OMVS,SHUTDOWN since
TCPIP is going to have to be quiesce along with other tasks. Why do I want
to do this? So I don't have to take an outage to make the change. I need to
create a couple more version root directories for cloning purposes.

Thanks much,
Gregg

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Scott Rowe

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Jul 20, 2010, 3:22:35 PM7/20/10
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I have changed my sysplex root from R/O to R/W without any problems, but I don't have much activity against my OMVS file systems. I don't think it really unmounts and remounts the file system, I think it just changes the attributes while it's mounted (using "Change attributes..." from the ISHELL Mount Table panel).

>>> Gregg Kimbrough <gregg.k...@BCBSFL.COM> 7/20/2010 2:41 PM >>>

Thanks much,
Gregg

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Veilleux, Jon L

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Jul 21, 2010, 7:31:33 AM7/21/10
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We have done this fairly often and have never experienced any problems with it.
Jon


Jon L. Veilleux
veill...@aetna.com
(860) 636-9179

Thanks much,
Gregg

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Mark Zelden

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Jul 21, 2010, 9:06:48 AM7/21/10
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On Wed, 21 Jul 2010 07:31:03 -0400, Veilleux, Jon L <Veill...@AETNA.COM>
wrote:

>We have done this fairly often and have never experienced any problems with it.

And it is a documented procedure:

http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/BPXZB291/7.5.1?SHELF=BPXZSH91&DT=20090112094853

http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/BPXZB291/7.5.2?SHELF=BPXZSH91&DT=20090112094853

My client runs 100% of the time mounted R/W in all the various sysplexes
using shared file systems. I guess since there is an established rotation for
new sysres sets, they probably could run with it R/O now and switch to R/W
when required.

The mode change wasn't even allowed until z/OS 1.5 (or z/OS 1.4 with a PTF).

That being said, I have never seen a single problem caused by having the
sysplex root mounted R/W 100% of the time.

If anyone in z/OS unix development is listening (or Peter), I think this
would make a good "best practice" health check.

Regards,

Mark
--
Mark Zelden - Zelden Consulting Services - z/OS, OS/390 and MVS
mailto:mze...@flash.net
Mark's MVS Utilities: http://home.flash.net/~mzelden/mvsutil.html
Systems Programming expert at http://expertanswercenter.techtarget.com/

Veilleux, Jon L

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Jul 21, 2010, 9:25:31 AM7/21/10
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Having the SYSPLEX root mounted R/W is NOT a best practice. This allows a malicious or uneducated user the chance to affect your system by filling up the SYSPLEX root zFS.


Jon L. Veilleux
veill...@aetna.com
(860) 636-9179


-----Original Message-----
From: IBM Mainframe Discussion List [mailto:IBM-...@bama.ua.edu] On Behalf Of Mark Zelden
Sent: Wednesday, July 21, 2010 9:06 AM
To: IBM-...@bama.ua.edu
Subject: Re: Using ISHELL to change the mount mode on the shared plex root?

http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/BPXZB291/7.5.1?SHELF=BPXZSH91&DT=20090112094853

http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/BPXZB291/7.5.2?SHELF=BPXZSH91&DT=20090112094853

Regards,

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Mark Zelden

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Jul 21, 2010, 10:03:16 AM7/21/10
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Jon,

I meant the exact opposite.

Now that you can switch the mode, I think it would be a good "best practice"
health check to see that the sysplex root is mounted read only.

Sorry that wasn't clear.

Mark
--
Mark Zelden - Zelden Consulting Services - z/OS, OS/390 and MVS
mailto:mze...@flash.net
Mark's MVS Utilities: http://home.flash.net/~mzelden/mvsutil.html
Systems Programming expert at http://expertanswercenter.techtarget.com/


On Wed, 21 Jul 2010 09:24:55 -0400, Veilleux, Jon L <Veill...@AETNA.COM>
wrote:

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Veilleux, Jon L

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Jul 21, 2010, 10:57:30 AM7/21/10
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Sorry I misread your answer.

Jon,

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Veilleux, Jon L

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Jul 21, 2010, 1:50:21 PM7/21/10
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By the way, I took a few minutes and wrote a REXX Health Check to make sure that the SYSPLEX Root is mounted R/O. It's not very difficult. Message table is the hardest part.

Jon,

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van der Grijn, Bart , B

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Jul 21, 2010, 3:21:25 PM7/21/10
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Jon, I thought the sysplex root had to be R/W. When I switch SYSRES
volumes a new entry is automatically created in the sysplex root at IPL
time. How does this work if you run your sysplex root RO?

The USS planning guide (1.10) has the following to say:

The sysplex root is used by the system to redirect addressing to other
directories. It is very small and is mounted read-write.

Bart

Mark Zelden

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Jul 21, 2010, 3:30:17 PM7/21/10
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On Wed, 21 Jul 2010 15:19:59 -0400, van der Grijn, Bart (B)
<Bvande...@DOW.COM> wrote:

>Jon, I thought the sysplex root had to be R/W. When I switch SYSRES
>volumes a new entry is automatically created in the sysplex root at IPL
>time. How does this work if you run your sysplex root RO?
>
>The USS planning guide (1.10) has the following to say:
>
>The sysplex root is used by the system to redirect addressing to other
>directories. It is very small and is mounted read-write.
>
>Bart

Read my post earlier. And yes, there is some ambiguity in the doc because
until z/OS 1.5 it did have to be R/W.

If you have an established set of sysres sets you swap between and don't
need to create a new directory in the root, then it can be RO now. If you
are going to IPL from a new sysres set, then you would need to change
the sysplex root to R/W prior to that IPL so the new version directory /
mount point can be created in the sysplex root. After that, you can
change it back to read only.

Mark
--
Mark Zelden - Zelden Consulting Services - z/OS, OS/390 and MVS
mailto:mze...@flash.net
Mark's MVS Utilities: http://home.flash.net/~mzelden/mvsutil.html
Systems Programming expert at http://expertanswercenter.techtarget.com/

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Mark Zelden

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Jul 21, 2010, 3:37:47 PM7/21/10
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On Wed, 21 Jul 2010 14:29:52 -0500, Mark Zelden <mze...@FLASH.NET> wrote:

>On Wed, 21 Jul 2010 15:19:59 -0400, van der Grijn, Bart (B)
><Bvande...@DOW.COM> wrote:
>
>>Jon, I thought the sysplex root had to be R/W. When I switch SYSRES
>>volumes a new entry is automatically created in the sysplex root at IPL
>>time. How does this work if you run your sysplex root RO?
>>
>>The USS planning guide (1.10) has the following to say:
>>
>>The sysplex root is used by the system to redirect addressing to other
>>directories. It is very small and is mounted read-write.
>>
>>Bart
>
>Read my post earlier. And yes, there is some ambiguity in the doc because
>until z/OS 1.5 it did have to be R/W.
>
>If you have an established set of sysres sets you swap between and don't
>need to create a new directory in the root, then it can be RO now. If you
>are going to IPL from a new sysres set, then you would need to change
>the sysplex root to R/W prior to that IPL so the new version directory /
>mount point can be created in the sysplex root. After that, you can
>change it back to read only.
>

For completeness, change the second sentence above to:

"If you are going to IPL from a new sysres set or add (IPL) a new system
into the shared file system environment..."

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