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Using BLSR to dicrease EXCPs for a VSAM file RRDS

 
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TitinaO

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Joined: 12 Mar 2007
Posts: 2
Location: Chile

PostPosted: Sat Dec 06, 2008 3:02 am    Post subject: Using BLSR to dicrease EXCPs for a VSAM file RRDS
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I am trying to optimize a process that has a lot of EXCPS. I am using subsystem BLSR to do that and it works fine for KSDS files , going from 2029 excps to 200 and 942 for 75.

But the problem is I have some RRDS files that has a lot EXCPs and even when I set the BUFND parm from a low value to a very high value (10-32000) I do not get a big change in the EXCPs.

Why BLSR is not working in this case ?? Am I missing something??

Thank you all for your help.
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Robert Sample

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Joined: 06 Jun 2008
Posts: 7931
Location: Bellevue, IA

PostPosted: Sat Dec 06, 2008 4:21 am    Post subject:
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From the VSAM Demystified Redbook (SG24-6105):
Quote:
Your application performance will improve using BLSR when direct access is
used and the same CI is referenced more than once in the processing. Using the
BLSR subsystem with sequential access could degrade performance rather than
improve it
And there is also in the same manual
Quote:
4.9.1 COBOL users take note
Note: This information was provided by Helen Witter.
Try to keep in mind is that COBOL is written for NSR processing. If anything is
done to switch the processing to LSR (whether OEM, SMB or BLSR), the
program or COBOL may not be able to handle it.
So if you're not accessing the same RRDS CI multiple times, you're not going to see much benefit to BLSR. And COBOL might prevent you from seeing any benefit, anyway.
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TitinaO

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Joined: 12 Mar 2007
Posts: 2
Location: Chile

PostPosted: Sat Dec 06, 2008 6:59 am    Post subject:
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Thanks for youre answer.
Hum.. That confuse me, because from Programming:
Batch Local Shared Resources Subsystem
Guide
Quote:
The VSAM data set types supported are:
Ÿ Key sequenced data set (KSDS)
Ÿ Relative record data set (RRDS), including variable RRDS (VRRDS)
Ÿ Entry sequenced data set (ESDS).


So it is supposed to handle RRDS files.. The ones I am trying to optimize.
DO you know a way to reduce the EXCPS for these files?
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Robert Sample

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Joined: 06 Jun 2008
Posts: 7931
Location: Bellevue, IA

PostPosted: Sat Dec 06, 2008 7:39 am    Post subject:
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The Redbook says BLSR handles RRDS but I'm not sure how much benefit RRDS can get from BLSR -- I've never dealt that much with RRDS to be able to say. Are you doing READ NEXT on the RRDS file or are you using the RELATIVE KEY for random access?
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