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mjadwani2785
New User
Joined: 28 Apr 2009 Posts: 89 Location: Noida , Dublin
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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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Joined: 27 Oct 2009 Posts: 2481 Location: Netherlands, Amstelveen
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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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Joined: 20 Oct 2006 Posts: 6966 Location: porcelain throne
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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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Joined: 27 Oct 2009 Posts: 2481 Location: Netherlands, Amstelveen
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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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Joined: 28 Apr 2009 Posts: 89 Location: Noida , Dublin
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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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Joined: 28 Apr 2009 Posts: 89 Location: Noida , Dublin
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oops wrong calculation above.. |
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Robert Sample
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Joined: 06 Jun 2008 Posts: 8696 Location: Dubuque, Iowa, USA
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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
Active Member
Joined: 31 Dec 2009 Posts: 580 Location: London
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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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Joined: 06 Jun 2008 Posts: 8696 Location: Dubuque, Iowa, USA
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Quote: |
Even a PDSE cannot exceed 65k tracks on a volume though, that is still a hard limit.
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Pete: check out DSNTYPE=LARGE, available since z/OS 1.7. |
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