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COBOL Filehanding IO operations

 
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DJN

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Joined: 04 Jun 2009
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Location: INDIA

PostPosted: Wed Jun 10, 2009 9:22 pm    Post subject: COBOL Filehanding IO operations
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I have a job running for 86 minutes to write total of 3 million records(into four files).
Can i speeden the IO operation?I read somewhere instead writing to file after each process .its efficient to move to a temp ws array then write at a strech. Is it sounding meaningful?
I tried doing so didn't notice any difference.
Someone can help me to find a better soultion .
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dbzTHEdinosauer

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Joined: 20 Oct 2006
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Location: porcelain throne

PostPosted: Wed Jun 10, 2009 10:16 pm    Post subject:
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what is your lrecl, blocksize, buffer count on dd statement?
dasd or tape?
qsam,vsam?
what kind of a computer/ops system?


Quote:
.its efficient to move to a temp ws array then write at a strech. Is it sounding meaningful?


since you are adding a move to table item (with the attendant index/subscript adjustment)
instead of simply to record area for the write,
I would imagine that it would add time, not save.
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Robert Sample

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

PostPosted: Wed Jun 10, 2009 10:56 pm    Post subject:
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Programs are either
- CPU-bound, meaning they're using all the CPU time they get and need more to continue, or
- I/O-bound, meaning they're waiting for I/O to be complete before they can continue.

The relevance is that if your program is CPU-bound, you can reduce the I/O time to zero and it would not have any impact on how long your program runs. So unless you have STROBE, APA, or another tool that will let you know if your program is CPU-bound or I/O-bound, you could be attempting to do the impossible.

If the job is not CPU-bound, things you can do to help reduce elapsed time include:
- adding buffers (at least a cylinder's worth) via DCB=BUFNO= or AMP= JCL statements to both input and output files
- running when little else is going on in the system
- running in a high priority batch initiator
- verify your files are not on high-traffic disk channels or packs
- don't write data if you don't have to -- the fastest I/O is the one you don't do

Considering you're reading 3 million to write 3 million, you're doing 6 million record processing in less than 1.5 hours, so the system isn't doing badly at all. One of our daily processes (that does not use a lot of CPU time) took 131 minutes yesterday to write 1,163,000 records -- but it does run when our system is busiest.
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DJN

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PostPosted: Thu Jun 11, 2009 2:12 am    Post subject: to dbzTHEdinosauer
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the files are in Disk.
And you are right its adding to the CPU time when i use a TEMP Array.

Thanks for ur suggestion
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DJN

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PostPosted: Thu Jun 11, 2009 2:22 am    Post subject: RoBert
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Hi Robert, Thanks for your suggestion.

Mine is not CPU bound
I wanna reduce CPU time. This job runs when our system is in busiest.(So it has to)

For 3 million records that too from various IMS parent child its doing good.


Thanks once again ; I will try if BUFNO can be of any use for me
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