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Query on BLSR


IBM Mainframe Forums -> JCL & VSAM
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Nileshkul

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Joined: 09 May 2016
Posts: 24
Location: India

PostPosted: Sat Aug 13, 2016 5:18 am
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Please help with a query on BLSR:
I have a 20 threads for a job running paralally. A VSAM file which has 20 copies used by 20 threads. That means each thread has dedicated copy file of VSAM.
NOW the same VSAM is using BLSR in all threads which I doubt why. Because each thread has it's own copy, there us no sharing of vsam copy file across threads or any other job. Will BLSR degrade performance in this case, Please suggest.
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Robert Sample

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Joined: 06 Jun 2008
Posts: 8568
Location: Dubuque, Iowa, USA

PostPosted: Sat Aug 13, 2016 8:05 am
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BLSR improves performances for random access of VSAM data sets (you do NOT have a "VSAM file" -- you have a VSAM data set; the only "files" on z/OS are on tape or in Unix System Services and neither of these can be VSAM). If the data set is being read sequentially, then BLSR won't improve performance (and may make it worse). Notice that the number of threads does NOT factor into whether or not BLSR can improve performance -- only the amount of sequential versus random processing.
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Nileshkul

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Joined: 09 May 2016
Posts: 24
Location: India

PostPosted: Sun Aug 14, 2016 12:48 am
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Got it now, thanks
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