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deepa12 · Posted: Tue Apr 05, 2005 12:04 pm Post subject: vsam alternate index

I have a doubt in the VSAM alternate index. I have learnt from 1 of the books that VSAM AIX is basically an ESDS. But off late the VSAM on OS/390 creates AIX as KSDS. Is there an option to create a KSDS or ESDS. Or is it that the upgraded version of VSAM always creates AIX as KSDS?
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deepa

kolusu · Posted: Tue Apr 05, 2005 1:01 pm Post subject:

Deepa12,

Can you share the source of the book where you learnt that an AIX is an ESDS? As far as I know an An AIX is a KSDS containing index entries organized by the alternate keys of its associated base data records. It provides another way of locating records in the data component of a cluster. An AIX can only be defined over a key-sequenced(KSDS) or entry-sequenced cluster.(ESDS)

It is a KSDS built by VSAM. An alternate index will contain the different alternate key values of a certain alternate key. For every alternate key field, a different alternate index is needed. The records in the data component contain an alternate key and one or more pointers to data in the base cluster. For an entry-sequenced base cluster, the pointers are RBA values. For a key-sequenced base cluster, the pointers are prime key values.

You can find the same info in this excellent IBM redbook about VSAM . read the chapter 1.3.12

http://publib-b.boulder.ibm.com/Redbooks.nsf/RedbookAbstracts/SG246105.html

Hope this helps...

Cheers

Kolusu
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Kolusu
www.linkedin.com/in/kolusu

deepa12 · Posted: Tue Apr 05, 2005 1:17 pm Post subject:

Thanks for your reply and the redbook pointer... But i will check the book...it will take 1 or 2 months since my books are in Chennai, india & am in UK
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deepa