Re: Latch Contention

> In regards to LATCH contention:
> I can't remember what they told us in "Oracle Tune and Troubleshooting
> Class" about multiple CPU's and the init.ora parameter
> "LOG_SIMULTANEOUS_COPIES"???? for copy latch. I can't remember what the
> instructor said that when adding a second or more CPU's that a latch
> parameter could be bumped up. Or was it spin_count?
> We have 2 250MHz Alpha CPU's, just added the second a couple months ago.
> (DEC UNIX 3.2)
> I just want to be optimal when we add another 50+ financial users.
>
> NAME GETS MISSES IMMEDIATE_GET
> IMMEDIATE_MISS
> -------------------- ---------- ----------
> ------------------------ --------------------------
> redo allocation 4865380 5915 0
> 0
> redo copy 0 0 0
> 0
>
> My current init.ora
> ========================
> log_small_entry_max_size 800
> log_simultaneous_copies 0
> spin_count 1
>
>

It looks like all copies are occurring on your redo allocation latch. The rule of thumb is that the misses/gets ratio should be less than 1%, which it is. If you wish to do the copies using the copy latch or latches more often, set:

log_small_entry_max_size - (smaller than 800, possibly 400) log_simultaneous_copies - (up to 2*CPU count, possibly 4)

Marg.

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