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How to find out how much free space is left in a vsam file

 
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morpheus007

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Joined: 27 Dec 2005
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PostPosted: Fri Oct 30, 2009 2:33 am    Post subject: How to find out how much free space is left in a vsam file
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I am trying to find out the amount of space used so far and the amount of space left in case of a vsam file.

Please let me know how to determine that.
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Bill Dennis

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Joined: 17 Aug 2007
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Location: Iowa, USA

PostPosted: Fri Oct 30, 2009 2:47 am    Post subject:
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After the file is CLOSED, run a LISTCAT and check the difference in HARBA and HURBA amounts.
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dick scherrer

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PostPosted: Fri Oct 30, 2009 2:49 am    Post subject:
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Hello,

How might this be a jcl question?

You might do a bit of research on LISTDSI. . . The forum search would be a good place to start.
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Robert Sample

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Joined: 06 Jun 2008
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PostPosted: Fri Oct 30, 2009 3:08 am    Post subject:
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The High Allocated RBA (HARBA) in a LISTCAT output gives the number of bytes allocated (technically, the offset to the highest allocated byte). The High Used RBA (HURBA) in a LISTCAT output gives the offset of the highest used byte; the difference is the amount of free space in the file. Is the free space usable? Good question with no easy answer. Maybe -- depending on (average) record length, CI size, CI free space percentage and CA free space percentage. Worst case is that none of the free space is usable -- for example, the record length is 1050 bytes (fixed), the CI size is 4096 and the CI free space percent is 20 percent -- which gives just over 800 bytes per CI free but it is not enough to write a record so none of the free space will be used.

The "amount of space left" in a VSAM file depends -- potentially a VSAM file can be 4 GB if not extended format, much larger if extended format. But the actual amount of space left (i.e., potentially allocatable space) can be affected by the number of extents already used, the number of disk packs the file is on, how many disk packs are candidate volumes, and so forth.

There is an excellent redbook on VSAM called VSAM Demystified that is well worth the time to go through.
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morpheus007

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PostPosted: Fri Oct 30, 2009 4:19 am    Post subject: Reply to: How to find out how much free space is left in a v
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thanks a lot for the help on this topic. Also i apologize for posting the question in the section.
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morpheus007

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PostPosted: Fri Oct 30, 2009 4:19 am    Post subject: Reply to: How to find out how much free space is left in a v
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Wrong section
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Robert Sample

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PostPosted: Fri Oct 30, 2009 4:45 am    Post subject:
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Glad to hear it helped -- and I've moved the topic.
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