Have you looked at adding BUFNI
and/or BUFND to the JCL DD ?
Do you have any vendor products doing VSAM tuning ? possibly doing buffer
tuning..
Regards,
Doug
Sent from my iPhone
On Apr 3, 2012, at 17:55, Steve Comstock <st...@trainersfriend.com> wrote:
> On 4/3/2012 3:23 PM, Frank Swarbrick wrote:
>> Current program does the following (in COBOL!).
>>
>> - Opens KSDS for I-O
>> - Sequentially processes another file (non-VSAM).
>> - For each record in the non-VSAM file it attempts a random (keyed) read of
>> arecord on the KSDS file. The key is, essentially, a concatenation of a
>> record
> type code ('4' or '5') and an account number. If no record of type '4' is
> found
> then it tries again for the same account, but with record type '5'. If either
> the '4' or '5' type is found it updates it and rewrites the record (assuming
> the
> data changed).
>>
>> This takes about 16 minutes to run. However if the 'type 5' logic is
>> removed,so that it only ever looks for type '4' records, it takes only about
>> one minute.
>>
>> Our resident VSAM expert says it has something to do with the VSAM "sequence
> set" and the fact that only one is kept in memory at a time. Since the same
> sequence set doesn't appear to be able to be used for both the 'type 4'
> records
> and the 'type 5' records it's constantly going back and forth, loading the
> "other" sequence set from disk. He says on VSE (which we were up until May
> 2010)
> more than one sequence set can be in memory, but with MVS this appears to not
> be
> the case.
>>
>>
>> Hopefully that reason is accurate. Is there a solution? We thought about
> having two COBOL FDs pointing to two DDs, where both DDs pointed to the same
> KSDS. This would probably(?) work, except for the fact of the update.
>>
>> Thanks,
>> Frank
>
> Well, I think we have a vocabulary problem. A VSAM KSDS only
> has one primary index, and the lowest level is the sequence
> set. You can't have two primary indexes, so you can only
> have one sequence set. It's not clear how your key is constructed,
> but you can get the whole sequence set in memory by using the
> right JCL DD parameters.
>
> First do a listc all against the cluster. Jot down these
> values: CI/CA for data component (shows as "PHYRECS/TRK"),
> and Levels in the index; then try this:
>
> if this process is batch, and no CICS processing is going
> on against the data set, consider adding:
>
> BUFNDI=#Index_levels,BUFND=(2*PHYRECS/TRK)+1
>
>
> If, on the other hand, your type '4' records are accessed as
> the primary key and your type '5' are accessed as part of
> an alternate index, you might need a different collection of
> DD parameters. (Long shot guess: add BUFNDI on the DD statement
> for your AIX).
>
>
>
> --
>
> Kind regards,
>
> -Steve Comstock
> The Trainer's Friend, Inc.
>
> 303-355-2752
> http://www.trainersfriend.com
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