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Sarangadhar

Hi all,
I observed one thing while I am keeping track of VSAM allocations daily. Till Yesterday 55 extents were allocated for my VSAM file. Now it became 60; it acquired 5 more extents.

My doubt is: When VSAM file acquires more extents? Is it when all the allocated extents are used?

If so there is a conflict; till Yesterday File aid was showing 65% used space. In IDCAMS LISTCAT ALL info HI-U-RBA is nearing HI-A-RBA. Why the difference in information between IDCAMS & File-Aid. I suspect File-Aid is giving wrong used space.
Which info is correct IDCAMS or File-Aid?
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Thanks

Bithead · Posted: Tue Oct 19, 2004 3:58 pm Post subject:

You are seeing CA splits aquiring more extents.

Not all CA will be full depending on your FREE SPACE paremeter so both FileAid and IDCAMS are probably correct.

You can reclaim the unused free space by running a reorg (REPRO to flat file, Delete/Define the VSAM and REPRO back). Note: if this is a database VSAM then use a valid reorg utility.

Sarangadhar · Posted: Tue Oct 19, 2004 4:58 pm Post subject:

Thanks Bithead, From your info I conclude this:
So, my VSAM file is having poor performance, right?
File aid is not considering the Unused freespace while showing used space.
It is just showing used space and Some space is lost in terms of unused free space right?
So, If we look at file-Aid used space and assumes the counterpart value as free sapce we will get misled right?
Any time free space=HIARBA-HIURBA, right?
More extents will be acquired only when the allocated extents are not having free space.

Are my conclusions are correct?
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Thanks

Bithead · Posted: Wed Oct 20, 2004 9:37 am Post subject:

I am no VSAM expert but I will give it a shot..

"my VSAM file is having poor performance, right? "

Not necessarily - performance may be OK, but you may have more free space that you need based on the rate that extents are being acquired and FileAid's analysis of usage. You should also determine how much space is unuseable based on CISIZE and RECORDSIZE.

"File aid is not considering the Unused freespace while showing used space. "

FileAid is show used space as a percentage of the total allocated volume. Used space would include data as well as CA and CI control data.

"It is just showing used space and Some space is lost in terms of unused free space right?"

The free space may not be lost, it may just be unused at this time.

"So, If we look at file-Aid used space and assumes the counterpart value as free sapce we will get misled right?"

It is a good indicator but you should do a full analysis of the file.

"Any time free space=HIARBA-HIURBA, right?"

Looking at the High RBAs is not necessarily a good indicator of the spave usage,

"More extents will be acquired only when the allocated extents are not having free space"

More Extents are acquired when a split is required but no space is available.

Sarangadhar · Posted: Wed Oct 20, 2004 9:57 am Post subject:

Thanks Bithead, U gave me info.
So, HI-U-RBA Gives the total Used space and the freespace that can not be used (Space that can not be used from this point).

How can we assess free space that can be used?
_________________
Thanks