Re: Redo Copy Latch Contention

Eric,
I'm a little bit happy to hear someone observed the same behavior about that latch. I posted something about that last week (see my note here after yours), but nobody answered. I'd be glad to know which release and O/S you have bad "redo copy" latch contention. Mines are 7.3.2 on a HP3000, MPE/iX. There are very few installation of Oracle on those mini-computer and I first thought my bad "redo copy" latch behavior was caused by the specific implementation of Oracle on MPE.

Michel Gauthier
Donohue Inc.

<miaemp_at_my-deja.com> wrote in message news:8383d8$tkf$1_at_nnrp1.deja.com...
> The last several days, I have been testing the effects of the
> LOC_SIMULTANEOUS_COPIES init.ora parameter to reduce Redo Copy Latch
> contention we are experiencing. Originally it was set to 12. I
> increased it to 24, the contention appeared to get slightly worse. I
> decreased it to 8, the contention appeared to decrease back to what it
> was when it was set at 12. Different performance tuning books have
> stated that the above init.ora parameter should be at least set to the
> number of processors on your system. Others have said that it should
> be up to 2 times the number of processors of your system.
>
> We are experiencing 94% misses on the Redo Copy Latches. These misses
> are primarily during nightly batch. Anyone have any ideas?
>
> TIA
> Eric Peterson
> Programmer/Analyst DBA
> eric_petersonNO_at_mauricesSPAMMERS.inrg.com
>
> Please note that any views I have expressed are purely my own and not
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>
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Michel Gauthier wrote (one week before...)
>I use to monitor latches to see if there are some contention on some of
>them. I can say that I'm proud of my database settings because, latches
wait
>ratios (misses divided by the gets) are almost all 0%, and when not,
they're
>less than 0.1 %... except for only ONE.
>The redo copy latch wait ratio is always greater than 80% !!! And I simply
>don't know why. I set up the log_simultaneous_copies to 6 (that is twice
the
>number of CPUs of our computer) as recommended.
>Does someone have a suggestion?
>
>Michel Gauthier
>Donohue Inc.
Received on Wed Dec 15 1999 - 07:26:24 CST