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What does space parameter values mean

 
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mjadwani2785

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PostPosted: Thu Sep 09, 2010 2:53 pm    Post subject: What does space parameter values mean
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Hi,

Please help me out with this one , one of my job is allocating datasets with the following attribute

DCB=(BLKSIZE=6144,RECFM=U),
DSNTYPE=LIBRARY,SPACE=(23200,(16999,3264,2625))

What does space parameter values mean what I can understand
23200 is avg rec length
2625 is dir blocks
what are the units for 16999 and 3264 ?
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PeterHolland

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PostPosted: Thu Sep 09, 2010 2:57 pm    Post subject:
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What is the manual saying you dont understand?
Or didnt you consult the manual?
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dbzTHEdinosauer

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PostPosted: Thu Sep 09, 2010 3:05 pm    Post subject:
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one thing, LIBRARY type - which is pdse,
you do not allocate Directory Blocks.
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PeterHolland

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PostPosted: Thu Sep 09, 2010 3:24 pm    Post subject:
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From DFSMS Using Datasets :

Your storage administrator can assign DSNTYPE=LIBRARY in the SYS1.PARMLIB member IGDSMSxx as an installation default value. If the installation default is DSNTYPE=LIBRARY, specify DSORG=PO or DIR space in the JCL or data class definition to allocate the data set as a PDSE (you do not need to specify DSNTYPE in this case).

But i understand its meaningless for PDSEs.
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mjadwani2785

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PostPosted: Thu Sep 09, 2010 3:27 pm    Post subject: space parameter !!
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to my correction after reading manual

23200 is avg block length in bytes
2625 is directory
16999 & 3264 are pri and sec data blocks in datasets.

total space allocated will be
16999+3264*15
=65959 blocks of 23200 blocklength in bytes
=733 cyl approx

Is my interpretation correct?
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mjadwani2785

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PostPosted: Thu Sep 09, 2010 4:36 pm    Post subject: space parameter !!
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oops wrong calculation above..
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Robert Sample

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PostPosted: Thu Sep 09, 2010 4:37 pm    Post subject:
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Quote:
total space allocated will be
16999+3264*15
=65959 blocks of 23200 blocklength in bytes
=733 cyl approx

Is my interpretation correct?
No, your interpretation is not correct.

First, a primary allocation may be filled by as many as 5 extents -- which reduces the number of secondary extents possible.

Second, The total space allocated initially will be the primary space only. Should the data set need secondary space, then up to 15 secondary extents (depending on the number of extents required to fulfill the primary space allocation) can be allocated. Only 16 extents are allowed on the pack, so if the primary space allocation required 5 extents then only 11 are available for secondary allocations.

So what you've provided is the absolute maximum that the data set can grow to on a single disk pack.

Furthermore, your conversion to cylinders is incorrect. 65959 blocks at 232000 bytes per block will place 2 blocks per track, or 30 blocks per cylinder. This means 2,199 cylinders will be required for the data set should it reach maximum size.
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Pete Wilson

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PostPosted: Tue Sep 14, 2010 7:39 pm    Post subject:
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It's getting complicated these days!

If it is a PDSE it can go to 123 extents on a volume.

Also extent consolidation may mean that an extra extent request is merged with the previous extent if there is contiguous space available next to it so that no further extent number is taken, just the previous one become larger.

Even a PDSE cannot exceed 65k tracks on a volume though, that is still a hard limit.
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Robert Sample

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PostPosted: Tue Sep 14, 2010 8:04 pm    Post subject:
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Quote:
Even a PDSE cannot exceed 65k tracks on a volume though, that is still a hard limit.
Pete: check out DSNTYPE=LARGE, available since z/OS 1.7.
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