DFHSM PDA log size calculation



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DFHSM PDA log size calculation

Postby Bad Man » Mon Jan 02, 2017 12:20 pm

Hi,

At our site the DFHSM PDA datasets keep getting swapped and archived to tape every 7 minutes(mostly), which I think is not good considering that the backup and swap may not be good at such short span of time, could cause contention.

Now I have been reading Implementation and customization guide but not able to find out how to calculate the appropriate size of PDA X and Y.

The present size of X and Y are 1661 cylinders.

Needed help on how to calculate an appropriate size and how many hours should be a good enough time to swap. On others sysplex systems it happens once in a day.
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Re: DFHSM PDA log size calculation

 

Re: DFHSM PDA log size calculation

Postby Robert Sample » Mon Jan 02, 2017 10:14 pm

My first response would be to ask why you've got active PDA data sets, anyway? PDA data sets record trace data to help debug HSM problems and there's probably not a whole lot of reason to routinely use the PDA data sets -- unless you routinely have HSM troubles that require a trace.

Second, IBM's Technote at http://www-01.ibm.com/support/docview.wss?uid=isg3T1012687 recommends sizing them to hold one to three hours of data before the swap. If you're getting 7 minutes, you need to make them 9 to 26 times as large as they currently are. And since they need to be on the same volume, that may limit how big you can make them even using a 3390 mod 54.
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Re: DFHSM PDA log size calculation

Postby Bad Man » Tue Jan 03, 2017 1:30 pm

A definition from the manual:
Problem determination aid log data sets
PDA log data sets provide you with trace information about DFSMShsm processing.

The DFHSM task that does the most processing will generate the most trace data. This DFHSM performs backup activity. Also we are doing round the clock recycles of magstar tapes. The trace entries are not problems
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Re: DFHSM PDA log size calculation

Postby Robert Sample » Tue Jan 03, 2017 6:23 pm

The trace entries are not problems
contradicts your earlier statement
the DFHSM PDA datasets keep getting swapped and archived to tape every 7 minutes(mostly), which I think is not good considering that the backup and swap may not be good at such short span of time, could cause contention.
So which is it -- are the swaps every 7 minutes an issue or not? You're getting swaps every 7 minutes BECAUSE of the count of trace entries -- so if the swaps every 7 minutes are a problem, then yes the trace entries are a problem; if the trace entries are not a problem, then you'll need to live with the swaps every 7 minutes (unless you increase the size of the data sets as stated earlier).
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Re: DFHSM PDA log size calculation

Postby Bad Man » Tue Jan 03, 2017 7:37 pm

ok Makes sense, we have decided to hold on until the recycle of tapes get over. THANKS
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