What do "DEFINE CLUSTER" and "zfsadm format" mean?

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What do "DEFINE CLUSTER" and "zfsadm format" mean?

Post by demecarv » Tue Sep 15, 2015 3:47 am

I am very new to Mainframe world and I need to support certain application which is published in DEV Mainframe and Prod Mainframe. Obviously, I can't move files from my PC to Prod so I need to move them from Dev Mainframe to Prod Mainframe. I am studying certain JCL script left by someone very experienced in Mainframe. The script is compound by many calls to shell scripts. After certain excellent help I received from other thread in this forum, I finally could found the scripts and most of them are very easy to understand for who has worked with Linux as java developer. Unfortunately, at the very begin there are two Shell commands that I am lost. I guess, but I am not sure, that "DEFINE CLUSTER" and "zfsadm format" is used here in order to set up a "temporary channel" between Dev Mainframe and Prod Mainframe (if I was in windows, I would say map a drive or map a folder from other server). I guessed this because I can see that the next step mount it. All commands below are ran in Prod called by certain JCL script.
From ibm.com/support/knowledgecenter I read:
DEFINE CLUSTER -> defines an entry-sequenced cluster that is used as a VVDS
zfsadm format -> Formats a VSAM linear data set as a zFS aggregate
Certainly, I missed basic knowledge and I just started to read "Introduction to the New Mainframe z/OS Basics" but I need to speed up my learning process. A basic explanation about the code below and an overview about VVDS, VSAM and zFS will help me to jump to the right topics.


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 zfsadm format -aggregate 'OMVS.SrvA.Dev.MyApp.TEMP.ZFS' -compat

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mount -f OMVS.SrvA.Dev.MyApp.TEMP.ZFS -t ZFS /tmp/MOVE/MyApp/Dev
Last edited by Anuj Dhawan on Tue Sep 15, 2015 9:40 am, edited 3 times in total.
Reason: Added code tags. Learn more about them at http://www.ibm-mainframes.com/faq.php#f3r0

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Re: What do "DEFINE CLUSTER" and "zfsadm format" mean?

Post by enrico-sorichetti » Tue Sep 15, 2015 4:00 am

but I need to speed up my learning process.
remember we reply on our own time and free of charge
if You have time constraints a forum is not the best place to ask for help.

also remember that a forum is not the substitute of proper training
and if You keep it going pretty soon people will be ignoring Your questions.

When I tell somebody to RTFM or STFW I usually have the page open in another tab/window of my browser,
so that I am sure that the information requested can be reached with a very small effort 8-)

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Re: What do "DEFINE CLUSTER" and "zfsadm format" mean?

Post by Robert Sample » Tue Sep 15, 2015 5:20 am

On a mainframe, it is possible to use Unix System Services under z/OS. Unix System Services has two file systems; HFS is older and less efficient and is being phased out by IBM; zFS is the replacement file system for HFS and has some advantages over HFS. A zFS data set is a special mainframe file called a VSAM linear data set (VSAM supports sequential, indexed, relative, and linear data sets -- they are all called VSAM data sets). The VSAM definition is done through a system utility called IDCAMS; DEFINE CLUSTER is the IDCAMS command to define a VSAM data set (in the case you posted, it is defining a zFS data set). Once defined, the zFS data set must be formatted before it can be used in Unix System Services. That is what the zfsadm format Unix System Services command is doing. Once defined and formatted, a Unix System Services mount command is used to associate the zFS data set with a Unix directory. After the mount command succeeds, all data written to the mount directory (or any directory below in the hierarchy) will be stored in the zFS data set. An unmount command will remove the association; after that data written to the mount directory will NOT be stored in the zFS data set but in whatever underlying data set (possibly the root data set).

If you have worked with Unix, much of Unix System Services will be fairly familiar. If you have not worked with Unix, then your learning curve will need to include enough Unix to understand the file system and mount points.

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Re: What do "DEFINE CLUSTER" and "zfsadm format" mean?

Post by Anuj Dhawan » Tue Sep 15, 2015 9:34 am

Adding about VVDS to the excellent and detailed explanation by Robert: VVDS stands for VSAM Volume Data Set and it’s a VSAM file that contains the information of all VSAM and SMS-managed non-VSAM data sets that reside on the volume where the VVDS file is allocated.

A VVDS is recognised by the restricted data set name SYS1.VVDS.Vvolser, where volser is the volume serial number of the volume on which the VVDS resides.

There is more to it - suggest you read more about there here: The VSAM Volume Data Set (VVDS)


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