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Re: latch contention

From: Alexey Ogol <lesha_at_crgu.com>
Date: Wed, 27 Jun 2001 12:46:27 +0300
Message-ID: <9hca03$2rpf$1@pandora.alkar.net>

> The total number of misses is very small compared
> to the total number of gets - however, the sleeps are
> very high compared to misses, so when you miss
> you miss it a lot. (Can I assume that the spin_gets
> on this latch was very low, can I also assume that
> you haven't reduced the _spin_count parameter ?)
Yes, sleeps are very high
and I haven't reduce the _spin_count

> Lost time is about 24 hours since database startup -
> I forgot to say that we needed to know how long the
> database had been up to gauge whether this was
> highly significant - and how many CPUs it was
> spread across.

Total number of cpu is 1
Database is running about 3 days

> Initially I would suspect a very busy block as the
> cause of the problem. Possibly even a couple
> that happen to be on the same latch. Have a look
> at v$latch_children (for cache buffers chains) to see
> if there are one or two latches with an individual
> high sleep count (start with >150000 as a guess).
>
> If there are one or two anomalous latches do:
> select obj, dbarfil, dbablk from x$bh
> where hladdr = {address of child latch}
>
> This gives you the data_object_id, and file/block
> of the blocks possibly causing the problem.
> This may give you some clues.

I tried to see latch_children for this latch There's two of them with sleep greater than 100000, total number of latches is 1024
But when I try to select from x$bh, i got "table or view does not exist" Received on Wed Jun 27 2001 - 04:46:27 CDT

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