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Does dd dsn=dummy save cpu cycles.

 
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bijoybabu83

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Joined: 15 Jan 2007
Posts: 36
Location: Kerala

PostPosted: Mon Dec 01, 2008 5:44 pm    Post subject: Does dd dsn=dummy save cpu cycles.
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I have to do some processing and write some data to a 5 files based on some conditions. But one file is no longer needed. So i put that file to dummy in the jcl like 'dd dsn=dummy' instead of DD DSN=&&SHORTS,DISP=(,PASS).

Will this save performance. Will this save cpu cycles.
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mmwife

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Joined: 30 May 2003
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PostPosted: Mon Dec 01, 2008 7:24 pm    Post subject:
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Hi Babu,

Yes, and more importantly, it eliminates the wait time inherent in writing data to a device.
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bijoybabu83

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Joined: 15 Jan 2007
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Location: Kerala

PostPosted: Mon Dec 01, 2008 8:15 pm    Post subject:
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Hi ,
Thanks for your Prompt help.

One more question I do have is will it take any CPU cycles if we put dd dummy.

Thanks,
Babu -
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Terry Heinze

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Joined: 14 Jul 2008
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Location: Richfield, MN, USA

PostPosted: Mon Dec 01, 2008 9:00 pm    Post subject:
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I don't think CPU cycles will be affected one way or the other. Where you save is I/O time which is where 99% of your time goes anyway. Also, CPU cycles aren't nearly as critical as they were years ago.
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dick scherrer

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Joined: 23 Nov 2006
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PostPosted: Mon Dec 01, 2008 10:05 pm    Post subject:
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Hello,

All "write"s take some cpu overhead - dummy uses the least.

If you are really interested in cpu use, you could change the code so that the file is no longer referenced in the code. The data moves/calculations to build the output "record" take more cpu than the dummy write. . .
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