Hi pablo,
try identifying the segments that are being contended
for using information of p1,p2 for buffer busy waits
and add more freelists for these segments. This
assumes that you have already separated your data and
indexes appropriately overe separate mount points.
As for enqueues leading to bbw .. my guesstimate would
be that oracle would not do this .. but instead wait
on another enqueue in this case .. correct me if i am
wrong here guys ..
hth
Deepak
- Pablo ksksksk <p_rodri99_at_yahoo.es> wrote:
> Hi list:
> I've been analyzing an instance's performance
> for
> some time. I found a lot of enqueue and a lot of
> buffer busy waits.
>
> Tracing the instance's sessions for some time I
> found
> that enqueue waits are mostly because of FK not
> being
> indexed. This of course generated shared locks
> (level
> 4) over child tables when a parent row was updated,
> deleted or inserted. I can solve this by creating
> the
> missing indexes.
>
> In reference to the Buffer busy waits, mostly of
> these
> waits takes place over TABLES and p3=0 in all cases.
> I think that p3=0 indicates that a session wants a
> block that is being read from disk by another
> session.
> Keeping the object in memory will solve this
> problem,
> but unfortunately this is not an option as I'm
> working
> with Oracle 7.3.4. and the tables are big. I think
> that a lot of queries are using these TABLES.
>
> The question is what can I do to solve this BBW?
>
> And another curiosity question, can enqueue waits
> generate buffer busy waits ? (as a session is
> waiting
> for some buffer that another session is holding in
> an
> incompatible mode)
>
>
> TIA
>
>
>
>
>
>
>
>
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Author: Deepak Thapliyal
INET: deepakthapliyal_at_yahoo.com
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Received on Tue Aug 14 2001 - 13:13:14 CDT
