VSAM Spacce allocated and used --> REXX

upendrasri · Active User Joined: 28 Sep 2017 Posts: 124 Location: India

Hi All,

There is a requirement in our environment where we have to Identify space allocated and used for all Vsam datasets (More than 20000 Data sets). And
We have to prepare report whose space utilization is < 10% .
As of now using LISTC we can get Allocated (HI-A-RBA) and Used space(HI-U-RBA). But when we check these allocated and used space information in File Aid its not matching. The below example of Listc of one of the dataset.

enrico-sorichetti · Posted: Sat Mar 09, 2019 4:14 pm

using the IGGCSI interface will be more effective than parsing the listcat output
search the forum for the examples ( IGGCSIRX )

upendrasri · Active User Joined: 28 Sep 2017 Posts: 124 Location: India

Hi Enrico,

Thanks for your quick response. I have gone through SYS1.SAMPLIB(IGGCSIRX) and looks bit complex to me. Is there any other way
to get VSAM Allocated and Used space information for a single Vsam dataset..

Thanks!

enrico-sorichetti · Posted: Sat Mar 09, 2019 4:46 pm

searching the forum with "IGGCSI*" returned 90' hits and at least one of them has what You need

upendrasri · Active User Joined: 28 Sep 2017 Posts: 124 Location: India

Hi Enrico,

I have executed one of the old rexx(From old forums search as suggested by you) which will provide the below information.
/* REXX ** RETURNS VSAM INFO, HARBA, HURBA, PHYRECSZ, RECS/TRK */

This information is same as LISTC information. But my query is these allocated and Used space details are different from File Aid ..

Just want to know what basis File aid is calculated Allocated and Used space details..

Thanks!

Nic Clouston · Posted: Sun Mar 10, 2019 3:32 am

Why not ask the File Aid creators? Why do you expect anyone here to have that sort of (proprietory) information?

upendrasri · Active User Joined: 28 Sep 2017 Posts: 124 Location: India

Hi Nic,

Actually am using formula (HI-U-RBA/HI-U-RBA) * 100 to find out used percentage of a Vsam file in my REXX. But Client is verifying this information using File Aid and lot of differences found in Usage percentage. And I know File aid is more accurate then LISTC.
I searched old forums and some one explained how file aid calculates Allocated space of Vsam file. But no information on Usage space calculation.
Just thought of checking in case if any body is having similar situation earlier..

Thanks!

upendrasri · Active User Joined: 28 Sep 2017 Posts: 124 Location: India

Here the link from old forums

www.ibmmainframeforum.com/vsam-sms/topic1171.html

Thanks!

Robert Sample · Posted: Sun Mar 10, 2019 9:55 am

Since you have no way to identify exactly how File Aid is doing the calculation, you'll just have to tell the client that your numbers are as close as you can get. If the difference is generally just a few percent, there's not really anything that should be done. If the difference is significant (such as 25% or more), then that would indicate a problem.

upendrasri · Active User Joined: 28 Sep 2017 Posts: 124 Location: India

Hi RoberT,

If I use HI-U-RBA and HI-U-RBA values the difference between file aid and LISTC is between 20 - 25%(which is high).

Thanks!

Robert Sample · Posted: Sun Mar 10, 2019 5:19 pm

You have started -- FINALLY -- to quantify the issue. You need to go further, though. Is the File Aid calculation larger or smaller than the LISTCAT calculation? Is the issue for every data set? If so, CONTACT THE FILE AID VENDOR FOR ASSISTANCE. If the issue only occurs for certain data sets, you need to identify for which data sets the issue occurs (small? large? SMS-managed?). After you've done this, you will still need to contact the vendor about the issue.

Since File Aid is not part of base z/OS, you really, really, REALLY need to start by contacting the vendor -- they know far more about their software than anyone on this (or any) forum.

upendrasri · Active User Joined: 28 Sep 2017 Posts: 124 Location: India

Hi Robert,

File Aid calculation is larger than LISTCAT. Yeah.. am contacting Vendor but not sure whether I can ask how File aid Calculates Allocated and Used space. But Am running FDR Reports to grab similar information.I will let you know more details.

Thanks!

David Robinson · Active User Joined: 21 Dec 2011 Posts: 199 Location: UK

IIRC, doesn't the LISTCAT output show the data at the point the dataset was last closed, or some other process that writes these stats. I may be off here, it's just a vague memory!

Perhaps File/Aid has a way of getting more "real time" information.

File/Aid can also run in batch, that might be an option for what you're after (although whether ALL File/Aid functionality is available in batch, I'm not sure).

upendrasri · Active User Joined: 28 Sep 2017 Posts: 124 Location: India

Hi All,

I ran FDR reports to extract Vsam utilization information. Not matching with File Aid but some what near to File Aid values.

Thanks!

steve-myers · Posted: Tue Mar 12, 2019 10:02 pm

Allocated space should match, ideally exactly.

Used space is much more complex. To some extent it depends on embedded free space, and actual CA and CI splits, and whether the calculation removes the defined embedded free space from HI-U-RBA.

The final issue is the relative reliability of HI-U-RBA and CA and CI splits. It's only recalculated every time the data set is closed. If the data set wasn't closed properly, say the system crashed or the address space updating the data set crashed, or possibly the application just abnormally terminated, these statistics are not going to be all that reliable.

expat · Posted: Wed Mar 13, 2019 1:05 pm

Given the above post, it may be useful to attempt to run a VERIFY on the cluster before getting the stats as that will, if the cluster is unallocated, OPEN / CLOSE the cluster and update the stats.

upendrasri · Active User Joined: 28 Sep 2017 Posts: 124 Location: India

Hi David,

Yes, we can use File Aid batch job to grab VSAM Information. I need to grab this information for almost 20,000 data sets which is bit tough. We dont have File Aid Batch option in our environment.

I have queried Vendor on Calculations used for Vsam Allocated and Used space information but didnt receive proper response from them.

Thanks!

upendrasri · Active User Joined: 28 Sep 2017 Posts: 124 Location: India

Hi Steve,

Yes , Allocated space is exactly matching. Looks like file is considering space inside CI's as well. File Aid information is more accurate than FDR and LISTC.

Thanks!

upendrasri · Active User Joined: 28 Sep 2017 Posts: 124 Location: India

Hi Expat,

I have created my own test file(Copied from prod file) and again ran verify against to it. Even then there is difference between LISTC and File Aid values.

Thanks!