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How to calculate the memory allocation of datasets

 
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viji_rags

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Joined: 04 Jun 2010
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PostPosted: Fri Jul 01, 2011 11:30 am    Post subject: How to calculate the memory allocation of datasets
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When I have to copy the input dataset to output dataset it abends due to space issue(B37). How can I calculate the exact number of cylinders to be allocated for the output dataset.

Viji.
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vasanthz

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PostPosted: Fri Jul 01, 2011 11:36 am    Post subject:
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This might be helpful
http://www.ibmmainframes.com/viewtopic.php?t=53305&highlight=
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Robert Sample

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PostPosted: Fri Jul 01, 2011 3:17 pm    Post subject:
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Terminology is critical in IT, where similar terms may mean very different things. Your post title asks how to calculate the MEMORY allocation of data sets. The answer is simple -- ZERO. Memory is used by the CPU to store programs and data used by the programs. Memory is not used -- EVER -- to store data sets. Memory is volatile and disappears the second the machine is reset or power lost. Memory is never measured in cylinders -- only in bytes. The only use of memory for data sets is the allocation of buffers to transfer data from memory to a disk volume or from a disk volume to memory, and again buffers are not measured in cylinders but in bytes.

Cylinders are used with disk volumes, which are -- very definitely -- NOT memory. If you search this forum for space allocation (all terms), you can find a number of posts that give formulas to calculate the amount of disk space required for a given LRECL, BLKSIZE and number of records.
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dick scherrer

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PostPosted: Fri Jul 01, 2011 8:45 pm    Post subject:
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Hello,

Quote:
How can I calculate the exact number of cylinders to be allocated for the output dataset.

Suggest you do NOT do this - unless the number of records can never change.

It is far more effective to calculate how much space is normally needed, allocate that as the primary allocation and then provide secondary space for when it is needed.

The best way for a process like this is that it never be seen again due to a space abend. . . .
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PeterHolland

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PostPosted: Fri Jul 01, 2011 11:09 pm    Post subject:
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WaysToFail ON

Always allocate the maximum, if the data fits you are lucky. If you overallocated then people like expat are going to kick your ...

WaysToFail OFF
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Marso

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Joined: 13 Mar 2006
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PostPosted: Sat Jul 02, 2011 11:35 am    Post subject:
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Try the LIKE or the REFDD parameter.
the space allocation (among other values that may be useful to you too) will be copied from the referenced dsname or ddname.
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expat

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PostPosted: Sat Jul 02, 2011 12:13 pm    Post subject:
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Peter, such actions are usually forgiven if the user remembers the RLSE parameter, and I of course have not forgotten to code the ACS for automatic space release icon_lol.gif
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PeterHolland

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PostPosted: Sat Jul 02, 2011 2:02 pm    Post subject:
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Somebody did an edit on my comment.

Well expat, i never used the RLSE parameter. But then the storage guys
and me are/were drinking buddies.
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