PY,SY Allocation for DASD



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PY,SY Allocation for DASD

Postby debo » Tue Jul 27, 2010 5:59 pm

Hi,

How the Py,Sy extends are allocated for a file ? Say for eg: SPACE=(TRK,(200,25))..
What is the max trks allocated for the above case ? 200 + 25*15 ? or 200 + 25 * 200 ?

Because i have created two datasets like this

Command - Enter "/" to select action Tracks %Used XT
TEST.TEST.DATA2 33 100 16 - GAVE PY = 1 & sy = 1 in option 3.2 ( max 023034 recs with 80 lrecl-if u add one more rec,its abending with SB37)

TEST.TEST.DATA3 37 100 16 - GAVE PY = 1 & sy = 0 in option 3.2 ( max 025826 recs with 80 lrecl-if u add one more rec,its abending with SB37)

Can you explain briefly how the PY,SY allocations are done exactly? how come it allocate 33 trks,when i give only 1 py & 1 sy ?
debo
 
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Re: PY,SY Allocation for DASD

 

Re: PY,SY Allocation for DASD

Postby Robert Sample » Tue Jul 27, 2010 6:08 pm

I am guessing -- and it is only a guess -- that PY means "primary" in your post, SY means "secondary". Please do not use abbreviations or terms that you do not see in other posts as using your own shorthand can cause more confusion and take longer to resolve that just using the correct, proper terms in the first place.

Space allocation does not just depend upon the SPACE= parameter. For SMS-managed data sets, the ACS routines can override and change your parameters so unless you know for sure whether or not the data set is managed by SMS you cannot say 100% for sure what is going on. In general, though, if you give SPACE=(TRKS,(200,25)) then the primary will be allocated at 200 tracks (in up to 5 extents) while up to 15 secondary extents of 25 tracks each can be allocated.

Both of your files have gone to 16 extents -- unless you delete and redefine them, you cannot add any more records to either one (although you could open for output and delete the existing records to reuse the existing space).
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Re: PY,SY Allocation for DASD

Postby debo » Tue Jul 27, 2010 6:29 pm

Hi,

thanks for your reply.Going forward i wont use abbrevations.
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Re: PY,SY Allocation for DASD

Postby debo » Tue Jul 27, 2010 6:42 pm

Hi,

I have another doubt..When i create the dataset in SORT jcl,its allocating max 16 tracks ( Primary = 1trks,secondary = 1 tracks) ....But when i create the dataset in 3.2 option with Primary = 1trks,secondary = 1 tracks, and if i edit records manually in 3. 4 option,it allocating maximum 33 tracks..How ?
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Re: PY,SY Allocation for DASD

Postby steve-myers » Tue Jul 27, 2010 7:56 pm

As Mr. Sample said, the System Managed Storage (SMS) control functions can mess with your specifications. This is probably what happened here. In my opinion, it's one thing to provide defaults, but ignoring what you specify is unacceptable.
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