When we went to pure virtual tape, this is what we got back from IBM DFHSM L2:
PARTIALTAPE(REUSE) vs PARTIALTAPE(MARKFULL)
When using a virtual tape system, IBM usually recommends using
PARTIALTAPE(MARKFULL).
RECYCLE
You (or automation) need to issue the RECYCLE command, it is not automatic.
Also, if you want HSM to recycle multiple tape volumes onto one, you will need
to use a GENERIC recycle command, for example:
Use 'ALL' to recycle both ML2 and backup tape volumes:
HSEND RECYCLE ALL PERCENTVALID(20) EXEC
Use 'ML2' to recycle only ML2 tape volumes:
HSEND RECYCLE ML2 PERCENTVALID(20) EXEC
Use 'BACKUP' to recycle only backup tape volumes:
HSEND RECYCLE BACKUP PERCENTVALID(20) EXEC
Suggested numbers for ML2RECYCLEPERCENT are 20% or 30%. This allows more
volumes to become eligible to be recycled onto fewer volumes at the same time.
For example:
VOL1 50%
VOL2 20%
VOL3 15%
VOL4 1%
With ML2RECYCLEPERCENT(1), only VOL4 will be recycled. The next time you run
RECYCLE again, the same tape would be recycled again and again. With
ML2RECYCLEPERCENT(25), VOL2, VOL3 and VOL4 would be recycled. The resulting
percent used for the output tape will become 36%, so, that tape will not be
recycled again the next time around.
MAXRECYCLETASKS(nn). Each recycle task requires an output tape. If you allow
5 recycle tasks to run concurrently and have 5 tapes to recycle, you will land
up with 5 recycled tapes (no reduction). If you increase the time between
recycles, this should also allow more tapes to become eligible to be recycled
onto fewer tapes.
If you have migrated to a new tape technology, the REUSE CAPACITY (this is an
average) will be incorrect leading to unneeded recycles. With time however,
the REUSE CAPACITY will better reflect the reality of your new environment.
Hope this helps.
Lizette
> -----Original Message-----
> From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On
> Behalf Of Anthony Fletcher
> Sent: Wednesday, March 02, 2016 4:20 PM
> To: IBM-MAIN@LISTSERV.UA.EDU
> Subject: HSM RECYCLE INFLUENCE
>
> We are using a VTS with the virtual tapes defined as 3490s, and we are using
> the recommended 'Mark TAPE Full' option. That's all well and good.
> It does, however, mean that there are a lot of 'tapes' and many of those may
> have a mixture of valid and no-longer-valid data sets - a call for Recycle.
> The VTS is probably under configured, but that's life, and its a financial
> institution so they keep everything for 7 years, and are paranoid about
> keeping things so there is really too much data floating around that has to
> continue to float around.
>
> HSM can decide that it should do recycles, and if it does decide, then it will
> according to its built in algrorithm.
>
> However, we find that the algorithm makes decisions based on the WHOLE set of
> volumes that it knows about. That is OK, except that if there are a lot of
> huge data sets that have been migrated, and they used full tapes (and probably
> more than one tape). That skews the data to a higher than the overall usage
> figure, and it doesn't conclude that recycles are needed. We can of course
> initiate manual recycles but working out which ones to choose is a pain. So we
> are looking at writing something to automate that. We are looking at reading
> the OCDS and using that to select which volumes (eg excluding the big ones)
> and then issue the RECYCLE commands.
>
> It seems that HSM ought to be able to automatically do the selection of which
> volumes to do in a way that works for us.
>
> So the question is whether we can influence the recycle trigger point
> automatically to select what to recycle? e.g. tell it to ignore the full
> volumes and only assess based on the rest of the volumes or something like
> that.
>
> We used to have real tapes and it didn't matter if the algorithm resulted in
> few recycles, but with the VTS we need to release the space in the VTS to stay
> alive.
>
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