See below

-----Original Message-----
From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf 
Of Donald Likens
Sent: Friday, November 22, 2013 1:14 PM
To: [email protected]
Subject: Managing the OMVS Root zFS FileSystem

We have 5 isolated systems running clones of our z/OS operating system. Our 
current zFS root file system has not been controlled and now we are now using a 
Serverpac to upgrade. I am planning to implement the maintenance procedure at 
the bottom of this message but first here are my questions:

1)  How do you control your root file system so that it is not updated?
>> always mount it read only

2)  How do you clone your root file system?
>> using DFDSS at the filesystem level.  Even on TECH, the root filesystem is 
>> mounted read only.   You should have a SMPE only base environment that never 
>> gets IPL'd that you apply your maintenance to.  Then clone everything to 
>> your sandbox for testing.  Too easy for unintended changes to get made to a 
>> root filesystem.  When doing maintenance, the maintenance root is mounted at 
>> /Service for the duration of the apply process, then unmounted when finished.

3)  Is it your understanding that /u and /usr/local are made available by IBM 
for our use?
>> possibly, but use those as a mountpoint only, for your own local filesystem.

4)  Does anyone see improvements to my planned procedure that follows?
>>Keep track of your root filesystem "modifications", and treat them as a 
>>usermod so that it is a repeatable process with future z/OS upgrades.
>>consider making all your filesystems ZFS (if not already) as that is the 
>>future, HFS is functionally stabilized.

With z/OS 1.13 we will name all USS file systems (including the root zFS ie. 
SYS1.OMVS.ROOT) that migrate with system maintenance to have a HLQ of SYS1 and 
that nothing other than what is shipped by IBM is located in the root zFS. 
Exception! To make this less impacting, we will add mount points already 
created to the root system each upgrade but future mount points will be added 
to the /u or /usr/local directories. We will have a two volume SYSRES (one 
containing PDSs the other containing USS files). The implementation process 
will be to IPL from SMPR13 and SMPF13, Make sure all is working well, Copy 
SMPR13 and SMPF13 over the production system res volumes, re-catalog the SYS1 
zFS datasets, and IPL. To support not having anything in the root, all future 
non-IBM mount points will be in the /u or /usr/local directories will be 
pointing to the SYS.U.zFS and SYS.local.zFS respectively. We will also explore 
making the root system read only on all systems other than the Tech LPAR (for 
system maintenance).

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