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File creation DASD vs TAPE - "No OPEN/WRITEs" in P

 
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manu
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Joined: 26 Dec 2002
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PostPosted: Thu Oct 06, 2016 4:34 am    Post subject: File creation DASD vs TAPE - "No OPEN/WRITEs" in P Reply with quote

Hi All,

I have a COBOL program that opens only certain output files based on parms in the JCL.I noticed that empty files are created in DASD even if the file is not opened in the COBOL program.But if in the JCL if i change the output to write to UNIT=CART,the files which are not opened in the program is not getting created.Can you please let me know the reason why empty files are created in DASD and not in TAPE(UNIT=CART).

I thought the files will get created only if the program issues open/writes statements.Thanks
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manu
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Joined: 26 Dec 2002
Posts: 47
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PostPosted: Thu Oct 06, 2016 4:40 am    Post subject: Reply with quote

Sorry the topic should read "File creation DASD vs TAPE - "No OPEN/WRITEs" in Program"
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William Collins
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Joined: 03 Jun 2012
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PostPosted: Thu Oct 06, 2016 12:09 pm    Post subject: Reply with quote

That's the way it works. The DASD data set cataloguing has nothing to do with a physical data set, CART/TAPE does.
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kolusu
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PostPosted: Fri Oct 07, 2016 9:49 am    Post subject: Reply with quote

manu,

The answer is SMS. If your shop has SMS (as most shops are) then your DASD allocations are handled by SMS and the dataset is allocated during the JCL scan process itself. So even if your program hasn't opened that particular DASD file, they are allocated via SMS. However with tapes, unless you OPEN ( Involves a Mount of the tape drive) the files are NOT created.
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