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Redo logs - need a guru

From: Steve Holdoway <steve_at_aethos.demon.co.uk>
Date: 1996/07/22
Message-ID: <4svvma$a6h_at_atlas.aethos.co.uk>#1/1 







Dear All,



Can anyone out there spread some light on how or if we can improve the
performance of our system. We are still benchmarking Oracle 7.2.3 on
HP-UX 10.10, using a 5 processor T520, and 14Gb of Mirrored disc ( 14
X 2 Gb discs over 4 controllers ). Nice toys, huh!



The bottleneck to the whole system seems to be the Redo logs. We have
tried up to eight redo logs of up to 1Mb in size, scattered out of the
way of the database. When benchmarking, the system sprints along until
it has filled up all of these, and then waits for the first one ( or
is it all ) to drain out before starting up. Or, in effect, the whole
system stops for about 30 seconds whilst it untwists its knickers.



We would prefer to have a degredation in absolute performance and a
constant throughput than this situation. Is there any way that we can
get the redo logs draining down and doing their bit whilst the main
application performs most of its work on the parts of the table that
are resident in the SGA?



If so, how do we do it? We found that bigger redo logs stopped the
system less often but for longer. Should we try using hundreds of
small redo logs? Or just run the Log Writer as a realtime process?



Any ideas will be gratefully received, the more off the wall they are,
the more fun we'll have in testing them!



The weirdest thing is that we're getting approximately the performance
that we expected out of this system, it just doesn't seem to be trying
at all!



TIA


Steve.
Received on Mon Jul 22 1996 - 00:00:00 CEST












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