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pshongal
New User
Joined: 14 Jun 2012
Posts: 96
Location: India
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Hi,
I have 2 files to be compared each having around 50MM records.
When I do this comparison on flat files, DFSORT takes less time, but when I do this using VSAM files, it takes more time.
I tested in test region with some 400K records (max record length=1450).
Both are variable length files.
Flat file comparison took 0.9 seconds
VSAM file comparison took 9.4 second.
Is there a way I can optimize this? |
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Nic Clouston
Global Moderator
Joined: 10 May 2007
Posts: 2455
Location: Hampshire, UK
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| Try using data sets rather than files. And why not try unloading the data sets and comparing the unloads? And those times - are they CPU or wall? |
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enrico-sorichetti
Superior Member
Joined: 14 Mar 2007
Posts: 10873
Location: italy
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it is common knowlege that VSAM processing is heavier than PS processing
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... why not try unloading the data sets and comparing the unloads?
And those times - are they CPU or wall? |
why read twice the input data ( repro + compare )
apart the extra disk space |
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pshongal
New User
Joined: 14 Jun 2012
Posts: 96
Location: India
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| As Nic mentioned, I have already tried by unloading VSAM and then compare. It works little better but not a huge impact because its double operation as Enrico mentioned |
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steve-myers
Active Member
Joined: 30 Nov 2013
Posts: 917
Location: The Universe
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In my opinion, Mr. Sorichetti's first sentence should read, "It is common knowledge that sequential VSAM processing requires more CPU time than an equivalent non-VSAM sequential data set."
In addition, you have to unload each data set (s-l-o-w) before the compare (much quicker). You really haven't gained anything! |
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enrico-sorichetti
Superior Member
Joined: 14 Mar 2007
Posts: 10873
Location: italy
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I stand corrected...
if it is the same for You I would prefer to sit corrected, it is more comfortable  |
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