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VSAM ESDS or RRDS

 
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rakesh.psnvnk
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PostPosted: Thu Sep 30, 2010 11:50 pm    Post subject: VSAM ESDS or RRDS
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can i overwrite (not append) records of same length in esds or in rrds vsam.
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superk

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PostPosted: Fri Oct 01, 2010 12:01 am    Post subject: Reply to: VSAM ESDS or RRDS
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Yes, of course.
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Bill O'Boyle

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PostPosted: Fri Oct 01, 2010 12:58 am    Post subject: Reply to: VSAM ESDS or RRDS
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If this is BATCH and you're attempting a direct READ on an ESDS record, using a specific RBA/XRBA, with intent on updating (or not), this can ONLY be done in ASSEMBLER.

However, for CICS/ESDS access, this can be done (regardless of the language) using the CICS FILE API's.

I can't speak for RRDS processing, due to limited exposure....

Bill
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superk

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PostPosted: Fri Oct 01, 2010 1:11 am    Post subject: Reply to: VSAM ESDS or RRDS
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Was I wrong? I thought COBOL supports a REWRITE for any of the VSAM formats, providing that they're opened in the correct (I-O) mode?
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Bill O'Boyle

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PostPosted: Fri Oct 01, 2010 1:58 am    Post subject: Reply to: VSAM ESDS or RRDS
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Kevin,

Even in Enterprise COBOL 4.2, the ability to issue a Batch ESDS direct READ (via an RBA/XRBA) is not supported. I would have thought by now, it would be part of the language?

I'm sure you can sequentially read records until you reach the one you need, but in a large file, this could take a while as you'd need to identify record-criteria after each READ as the associated RBA/XRBA is unknown to COBOL.

IIRC, there's a way around this by defining the ESDS Base Cluster with an alternate index, but CRS has set in and I my recall factor has very much diminished. icon_redface.gif

Maybe Batch RBA direct READ's can be done in Enterprise PL/I icon_question.gif

Somebody else probably knows the alternate index trick for COBOL.... icon_wink.gif

Bill
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Akatsukami

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PostPosted: Fri Oct 01, 2010 2:41 am    Post subject: Re: Reply to: VSAM ESDS or RRDS
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Bill O'Boyle wrote:
Maybe Batch RBA direct READ's can be done in Enterprise PL/I icon_question.gif

Don't think so, although if your records are of fixed length you could kludge up a record number as FLOOR(RBA/record_length)+1
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Bill O'Boyle

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PostPosted: Fri Oct 01, 2010 3:00 am    Post subject: Reply to: VSAM ESDS or RRDS
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Yes, you could take a SWAG at building an RBA/XRBA, but if the given HLL can't (under the covers), infiltrate the given ACB/RPL, you're back to square one.... icon_wink.gif

The Enterprise COBOL for z/OS V4.2 Programming Guide (SC23-8529-01), section "1.10.2.4 Specifying access modes for VSAM files", states -

Quote:

You can access records in VSAM sequential files only sequentially. You can access records in VSAM indexed and relative files in three ways: sequentially, randomly, or dynamically.

Unless I'm interpreting this incorrectly, ESDS Direct READ's by RBA/XRBA, of the Base Cluster, are not supported.

One would have to assume that after all these years, this ability would be supported <sigh>? icon_sad.gif

Bill
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