A few weeks ago I raised a query about database unload/load timings and if
they have any effect on improving large restore performance.
Well, I have now been through the exercise and for anyone else thinking about
this here are
my results.
TSM 3.7.20.0
OS390 2.8.0
Database size was 84.4% utilised of 18612 mb.
After unload/load database was 54.1% utilised
Unload elapsed time was 11 hours
Load elapsed time was 4 hours.
Subsequent client restore test produced a restore saving of 1 hour 17 minutes
(novell client 17 gb. of data 1.5 million objects restored)
No, I did not down my production TSM for 15 hours plus.
I cheated.
I restored my latest full production database onto my development TSM system
and did the load unload and client restore test there.
But the test was valid because the production and development TSM are on
separate logical
partitions on the same physical OS390 machine, and the development TSM can read
but not write the production TSM tapes.
I am not convinced that I will do this exercise on our production TSM because
of the TSM unavailable time, and because I am not sure how long the restore
saving would last before database fragmentation was as bad as before.
Hope this information is of use to anyone contemplating this process.
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