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manu Beginner
Joined: 26 Dec 2002 Posts: 47 Topics: 19
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Posted: Thu Oct 06, 2016 4:34 am Post subject: File creation DASD vs TAPE - "No OPEN/WRITEs" in P |
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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 Beginner
Joined: 26 Dec 2002 Posts: 47 Topics: 19
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Posted: Thu Oct 06, 2016 4:40 am Post subject: |
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Sorry the topic should read "File creation DASD vs TAPE - "No OPEN/WRITEs" in Program" |
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William Collins Supermod
Joined: 03 Jun 2012 Posts: 437 Topics: 0
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Posted: Thu Oct 06, 2016 12:09 pm Post subject: |
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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 Site Admin
Joined: 26 Nov 2002 Posts: 12359 Topics: 75 Location: San Jose
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Posted: Fri Oct 07, 2016 9:49 am Post subject: |
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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. _________________ Kolusu - DFSORT Development Team (IBM)
DFSORT is on the Web at:
www.ibm.com/storage/dfsort
www.linkedin.com/in/kolusu |
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