MAXSCRATCH head puzzler

[n9kws]

Hi All --

I am looking for somebody to explain to me the terms & conditions of the MAXSCRATCH value in the stg definition.

I have a v5.5 server I inherited which is currently in a state where MAXSCRATCH < Total Number Used (ie MAXSCRATCH = 500 < Number Used = 1300+). I am under the impression that this should not be possible. How is this happening, and what do I look at to determine the cause?

Additional info, the volumes in question are not in a pending state, have data on them, and are in the library. If there is anything else just ask I will try to get an answer.

Any light you can shed on this odd happening would be appreciated.
Andy.

 

[GregE]

If your NUMSCRATCHUSED is greater than MAXSCRATCH, it's because someone set the MAXSCRATCH=500 after the NUMSCRATCHUSED was already 1300. If you are already using 1300, it will not move data off of 800 tapes to get the stg pool back to 500, but if NUMSCRATCHUSED is 500 and your MAXSCRATCH is 500, TSM will not use any more than 500.

 

[n9kws]

Thanks for responding, if I am reading the last part of your answer correctly it sounds like the tape volumes > MAXSCRATCH are now in a suspended state since the total used is now greater than MAXSCRATCH. Is that correct?

Andy.

 

[madbug0]

Yes,
Now it should remain in suspend mode and will not increase the tape count in that stg above 1300.

 

[GregE]

Thanks for responding, if I am reading the last part of your answer correctly it sounds like the tape volumes > MAXSCRATCH are now in a suspended state since the total used is now greater than MAXSCRATCH. Is that correct?

Those extra 800 are not "suspended" in any way. NUMSCRATCHUSED won't go over the current 1300, but those tapes can be written to as any other can be. So you have 1300 used in that pool, with 500 as your MAXSCRATCH. This means that TSM will get another empty scratch to use and go to 1301. And, for example, if you move data off of 2 of those tapes, you now have 1298 used. TSM will NOT go get another empty scratch tape to get to 1299 because your MAXSCRATCH is still only 500.

With your current NUMSCRATCHUSED=1300 and MAXSCRATCH=500, TSM will not define any more empty scratch tapes to that pool, until....1) your MAXSCRATCH is set >=1301 .....OR.....2) you move data off of 801 of the 1300 tapes, leaving a NUMSCRATCHUSED <=499.

 

[madbug0]

Those extra 800 are not "suspended" in any way. NUMSCRATCHUSED won't go over the current 1300, but those tapes can be written to as any other can be. So you have 1300 used in that pool, with 500 as your MAXSCRATCH. This means that TSM will get another empty scratch to use and go to 1301. And, for example, if you move data off of 2 of those tapes, you now have 1298 used. TSM will NOT go get another empty scratch tape to get to 1299 because your MAXSCRATCH is still only 500.

With your current NUMSCRATCHUSED=1300 and MAXSCRATCH=500, TSM will not define any more empty scratch tapes to that pool, until....1) your MAXSCRATCH is set >=1301 .....OR.....2) you move data off of 801 of the 1300 tapes, leaving a NUMSCRATCHUSED <=499.

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Agreed with GregE, those volumes will not be in suspended mode, but will be used for that storage pool data. It will not go further to 1301 and if space reclamation will run, it will start decreasing the no. of volumes used.

So you just need to wait for some time to get the volume levels come below 500.