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Optimal Space parameters for a dataset

 
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Vasanthr

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Joined: 24 Jan 2011
Posts: 21
Location: India

PostPosted: Fri Jan 23, 2015 9:13 am    Post subject: Optimal Space parameters for a dataset
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Hi Everyone,

I have a dataset with around 60 million records. Everyday this file gets updated and written to a new file in the program with some records added to it. This takes
almost everyday 20 minutes to complete. I see the below message in SYSMSG for multiple volumes and I believe if I could adjust the space parameter , I could make this job to run little faster.



Code:
REDUCES FOR DD=SYS155 DSN=PRD.ILM.XTGSPEC.G5961V00 VOL=L91793 POOL=PR
SECONDARY SPACE REDUCED FROM 700 TO 140 CYL
REDUCES FOR DD=SYS155 DSN=PRD.ILM.XTGSPEC.G5961V00 VOL=L91793 POOL=PR
SECONDARY SPACE REDUCED FROM 700 TO 140 CYL
REDUCES FOR DD=SYS155 DSN=PRD.ILM.XTGSPEC.G5961V00 VOL=L91996 POOL=PR
SECONDARY SPACE REDUCED FROM 700 TO 98 CYL
REDUCES FOR DD=SYS155 DSN=PRD.ILM.XTGSPEC.G5961V00 VOL=L91996 POOL=PR
SECONDARY SPACE REDUCED FROM 700 TO 92 CYL
REDUCES FOR DD=SYS155 DSN=PRD.ILM.XTGSPEC.G5961V00 VOL=L91996 POOL=PR
SECONDARY SPACE REDUCED FROM 700 TO 91 CYL
REDUCES FOR DD=SYS155 DSN=PRD.ILM.XTGSPEC.G5961V00 VOL=L91996 POOL=PR
SECONDARY SPACE REDUCED FROM 700 TO 38 CYL
REDUCES FOR DD=SYS155 DSN=PRD.ILM.XTGSPEC.G5961V00 VOL=L91996 POOL=PR
SECONDARY SPACE REDUCED FROM 700 TO 12 CYL
REDUCES FOR DD=SYS155 DSN=PRD.ILM.XTGSPEC.G5961V00 VOL=L91996 POOL=PR
SECONDARY SPACE REDUCED FROM 700 TO 6 CYL
REDUCES FOR DD=SYS155 DSN=PRD.ILM.XTGSPEC.G5961V00 VOL=L91996 POOL=PR
SECONDARY SPACE REDUCED FROM 700 TO 2 CYL
REDUCES FOR DD=SYS155 DSN=PRD.ILM.XTGSPEC.G5961V00 VOL=L91996 POOL=PR
VOLUME HAS NO FREE SPACE
REDUCES FOR DD=SYS155 DSN=PRD.ILM.XTGSPEC.G5961V00 VOL=L92233 POOL=PR
SECONDARY SPACE REDUCED FROM 700 TO 95 CYL
REDUCES FOR DD=SYS155 DSN=PRD.ILM.XTGSPEC.G5961V00 VOL=L92233 POOL=PR
SECONDARY SPACE REDUCED FROM 700 TO 85 CYL
REDUCES FOR DD=SYS155 DSN=PRD.ILM.XTGSPEC.G5961V00 VOL=L92233 POOL=PR



file is defined in JCL as below

Code:
//             DISP=(NEW,CATLG,DELETE),BUFNO=40,
//             UNIT=&UNITD,
//             SPACE=(CYL,(1400,700),RLSE),VOL=(,,,25),
//             LABEL=,
//             DCB=(&MDSCB,RECFM=VB,LRECL=1254,BLKSIZE=0),
//             MGMTCLAS=GDGBKUP0



Please help me with providing optimal space parameters in the JCL
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steve-myers

Active Member


Joined: 30 Nov 2013
Posts: 574
Location: The Universe

PostPosted: Fri Jan 23, 2015 9:45 am    Post subject:
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We here, in this forum, can't respond to this very well, for several reasons.
  • About the only SPACE attribute that might make even the slightest performance improvement is the unit of allocation, and CYL is about the best you can do.
  • It takes a small amount of time to add an additional extent to a data set. Obviously if this can be bypassed you're ahead of the game.
  • Similarly, it takes a small amount of time to do a volume switch. Again, if it can be bypassed, ...
  • The messages you're showing are coming from some sort of product that is not known to me. Some of these messages suggest, to me, that it is operating in a fashion to damage your goal. You must discuss this with your support.
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Robert Sample

Global Moderator


Joined: 06 Jun 2008
Posts: 8165
Location: East Dubuque, Illinois, USA

PostPosted: Fri Jan 23, 2015 8:24 pm    Post subject:
Reply with quote

Quote:
I believe if I could adjust the space parameter , I could make this job to run little faster.
The VAST majority of the 20 minutes is being spent reading 60 million records and writing 60 million records. Tweaking allocation parameters is not likely to make much of a difference in your elapsed time -- but feel free to try.

However, your BEST bet is to work with your site support group. Their storage people may have suggestions (such as creating a separate storage pool or moving your data set into a different storage pool) that you haven't thought of and do not have the authority to implement if you did think of them.
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