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How to Calculate No of members in a pds?

 
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pkmurali
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PostPosted: Tue Jun 27, 2006 4:35 pm    Post subject: How to Calculate No of members in a pds?
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Hi All,
Let me like to know to calculate Number of Members in a pds Based on Primary Space(PS),Secondary Space(SS) and directory space(DS).For Example, A pds having PS=20,SS=20 & DS=400 what is the maximum number of members we can store in a pds?
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cpuhawg

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PostPosted: Tue Jun 27, 2006 7:53 pm    Post subject: Re: How to Calculate No of members in a pds?
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Each directory record may contain 6 members, so setting the directory space to 400 would allow for about 2400 members.

This number of members would be independant of the primary and secondary space allocations. A member can be empty, contain 1 record, or 10 of thousands of records, so there is no way to know a maximum number of members. As members are added to the PDS, the PDS would take additional extents of 20 until all available space is used up and maximum extents are reached. At this point, attempting to save a member may result in a S-E37 abend which would indicate the PDS needs to be compressed.
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ofer71

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PostPosted: Wed Jun 28, 2006 12:38 pm    Post subject:
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cpuhawg - Unless you use PDS-E...

O.
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rexxhead

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PostPosted: Mon Jul 24, 2006 10:05 pm    Post subject: Re: How to Calculate No of members in a pds?
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cpuhawg wrote:
Each directory record may contain 6 members, so setting the directory space to 400 would allow for about 2400 members.


A directory entry is 256 bytes. ISPF stores about 40 bytes of directory data for each member, so for a dataset where all the members have ISPF statistics, the answer is '6'. The minimum space required for a directory entry is about 12 bytes so you can fit 20+ members/block if they are 'plain vanilla'. There will always be an entry for 'FFFFFFFF'x so the number of real members that can be stored is typically one fewer than calculated.

A 3390-equivalent will hold 43 directory blocks per track and directory space is always allocated in full tracks, so it makes sense to ask for directory blocks in multiples of 43.
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muthusamy

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PostPosted: Mon Dec 01, 2008 6:26 pm    Post subject:
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Max no of members for a pds is calculated by the following formula
Max=(6*n)-1 where n is the no of directory blocks

If n=1 then max no of members for a pds=(6*1)-1=5
If n=2 then max no of members for a pds=(6*2)-1=11

I checked above answers by manually creating members in Mainframe.
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