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More than 16 extents possible for a PS file?


IBM Mainframe Forums -> JCL & VSAM
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anjoos20

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Joined: 09 Apr 2008
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PostPosted: Thu May 03, 2012 2:58 pm
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I have read every where that max 16 extents are possible for a PS file. But I could see used extents :23 for a particular PS file in our system. Could any one please clarify?

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no reason to waste 128 KBytes when a plain text cut and paste would just use 3 KBytes
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Bill Woodger

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Joined: 09 Mar 2011
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PostPosted: Thu May 03, 2012 3:09 pm
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Please don't post screenshots. Copy & paste from your emulator. Use the Code tags to format the output.

Do you see the + next to the volume? Means there is more than one volume, where you will find you other extents.
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Akatsukami

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PostPosted: Thu May 03, 2012 3:14 pm
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Please do not post screenshots, as they are wasteful of space; instead, copy and paste, enclosing the pasted information in Code tags.

Only sixteen extents (primary and 15 secondary) extents are permitted per volume. However, as the plus sign next to the volume serial number indicates, this data set extends over multiple volumes. A total of 59 volumes is allowed; thus a total of 59*16 = 944 extents may be realized.
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Pete Wilson

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PostPosted: Thu May 03, 2012 5:28 pm
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If a DSORG=PS dataset has an Extended Format Dataclas then it can have 123 extents per volume and spread across a maximum 59 volumes = 7257 extents theoretical maximum.
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Pete Wilson

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PostPosted: Thu May 03, 2012 5:58 pm
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ps: The example you show has LRECL=80,BLKSIZE=80 and is using 30,000 trks which is not very intelligent.

Suggest you reallocate the file ommitting BLKSIZE (or coding it as BLKSIZE=0) which results in an SDB (System Deteremined Blksize). You'll find the file should be much smaller after that.
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Pete Wilson

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PostPosted: Fri Jun 15, 2012 12:57 am
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DSNTYPE=LARGE format PS files can also have more than 16 extents, and can exceed the 65k tracks per volume limit like the Extended format datasets.

IBM recommend using these for SORTWK's.
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