Roach, Dennis wrote:
RMM is a tape management (inventory) system (TMS). It makes no difference if
the tape is real or virtual. All TMSs and VTSs that I know of work together.
The savings with VTS are:
1. If it is tuned correctly, the mount time should be zero for most mounts. If
a lot of tapes are having to be recalled from the multi-volume tape to DASD,
the cache management tuning has a problem of the cache size is to small.
2. Disaster backup has become a lot easier. We send a full copy of the entire
virtual tape system offsite monthly. Make sure that anything needed for a
base IPL is on real tape for stand alone restore.
3. The footprint and environmentals are better. We went from 6 silos to 2 with
a major power and heat reduction.
1. The same apply for non-VTS configuration. We just *avoid* tape
mounts. Obviously the tapes still have to be mounted for HSM usage, but
- according to the tape capacity - this is not big issue. We mostly do
backups. Restores are much less frequent, mostly ML2 recalls.
For environments, where restores are really frequent (development,
tests) VTS could be better solution. Alternatively, it is worth to
consider backups on DASD. Of course it should be *cheap* DASD and amount
of data cannot be huge.
2. I'd prefer remote copy DASD to DASD. Even if you have to use tape,
you still can have many DASD volumes dumped on single tape cart, no need
for virtual volumes. At the price of VTS you can probably buy another
library, remotely connected and do duplex copies online. RPO would be
much better.
BTW: I was informed, that reading directly from stacked tape (without
VTS) is possible, but time consuming.
3. IMHO it's unrelated to VTS usage, unless you had problem with tape
utilisation. This problem probably can be solved using TMM or by changes
to JCL.
--
Radoslaw Skorupka
Lodz, Poland
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