Chris,
You should see the waits in V$SESSION_EVENT as well, as these are rolled in
to the V$SYSTEM_EVENT. You have to query V$SESSION_EVENT when these thread
are active. And you will have to query it repeatedly as it reports waits as
and when session encounters some.
I would also consider the impact on all the indexes for table where data is
getting inserted. It will cause contention if all these processes are
inserting index entries in the same general area. Reverse indexing may help
some. I can comment much, as I have not yet used them in a production setup.
Good luck,
- Kirti
-----Original Message-----
Sent: Wednesday, January 16, 2002 12:48 PM
To: Multiple recipients of list ORACLE-L
Thanks Kirti and Paul for the reply.
The instance is up for only 3 days. We know there are
very heavy inserts in the database.
Yes, There are high waits for 'buffer busy waits'
event in V$SYSTEM_EVENT view. But I didn't see 'buffer
busy waits' in V$SESSION_EVENT. I may try to increase
the freelist to 12(I don't know whether it helps,
anyway we have 12 Java threads insert data into the
same table concurrently).
Thanks,
Chris
- "Deshpande, Kirti" <kirti.deshpande_at_verizon.com>
wrote:
> How long has the instance been up?
>
> It appears that the application is trying to read
> the same data blocks &/or
> more sessions are trying to update the same data
> block or the free lists may
> need to be set properly to support concurrent
> INSERTs.
>
> So, before changing anything for DBWR process, I
> would suggest to check the
> top wait events from V$SYSTEM_EVENT view. You may
> see high waits for 'buffer
> busy wait' event. If so, I would trace it further
> using V$SESSION_EVENT and
> V$SESSION_WAIT (P1, P2 values) to find out the 'hot'
> segment and the file.
> You may have to review the pctfree, freelists,
> extent sizes etc. to address
> 'buffer busy waits'.
>
> For all you know, it could be just an application
> issue in scheduling the
> processes properly.
>
> And to answer your question about setting
> DBWR_WRITE_PROCESSES(actually the
> parameter is DB_WRITER_PROCESSES) you may want to
> check out Note# 97291.1 on
> Metalink. It has some good information.
>
> HTH,
>
> - Kirti
>
>
> -----Original Message-----
> Sent: Tuesday, January 15, 2002 7:16 PM
> To: Multiple recipients of list ORACLE-L
>
>
> Hi, gurus:
> The database is oracle8.1.7.2.1 on win2k machine
> with 1 CPU and two hard drives. When I query
> v$waitstat, I got the following:
>
> CLASS COUNT TIME
> ------------------ ---------- ----------
> data block 246901435 132690159
> segment header 4869 8018
> undo block 20986 38476
> undo header 1895 1556
>
> seems like I need to set DBWR_WRITE_PROCESSES to a
> higher number, what number should I choose, 2 or
> bigger?
>
> Also, what other problems can you see from the last
> query, other than we need to add some more RBS?
>
> Thanks,
>
> Chris Harvest.
>
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Received on Wed Jan 16 2002 - 13:46:59 CST
