Re: Re: what's mean of "enqueue hash chains" latch?
- From: "biti_rainy" <biti_rainy@xxxxxxxxx>
- To: "oracle.unix@xxxxxxxxx" <oracle.unix@xxxxxxxxx>, "Peter.Hitchman@xxxxxxxxxxx" <Peter.Hitchman@xxxxxxxxxxx>
- Date: Sun, 9 Jan 2005 12:56:00 +0800
hi,eygle
show us the v$waitstat ?
anyway , increase the number of freelists and freelist group may or
may not be helpful. if you can ,just have a try.
btw:
with multiple freelist groups,need recog the segment, the freelists header
of a group can use a separate block,not the segment header ,2 groups use
2 separate blocks. NONE OPS can use multiple freelist groups too,it would
reduce the contention of the segment header.
Best regards
msn: biti_rainy@xxxxxxxxxxx
a dba from alibaba(china)
---- from the mail-----
>Thanks Pete;
>
>In fact ,at that moment ,only the operation is excute in databasee.
>So ,no often commit ,from statspack report:
>
>user calls 914 1.1 914.0
>user commits 1 0.0 1.0
>
>And the logfile is big enough,from statspack report:
> Avg
> Total Wait wait Waits
>Event Waits Timeouts Time (cs) (ms) /txn
>---------------------------- ------------ ---------- ----------- ------ ------
>PX Deq Credit: send blkd 1,564 1,564 320,620 2050 ######
>PX Deq: Execute Reply 391 391 80,155 2050 391.0
>latch free 7,537 7,537 16,303 22 ######
>control file parallel write 258 0 669 26 258.0
>db file sequential read 505 0 132 3 505.0
>log file sync 1 0 9 90 1.0
>log file parallel write 4 0 8 20 4.0
>
>and
>
>DBWR buffers scanned 0 0.0 0.0
>DBWR checkpoint buffers written 0 0.0 0.0
>DBWR checkpoints 0 0.0 0.0
>DBWR free buffers found 0 0.0 0.0
>
>I am agree that we may need to increase freelists for parallel
>operation,but at that monment,we have no "Buffer wait Statistics"
>output from statspack.
>
>thanks for you info,it's useful to me.
>
>On Sat, 8 Jan 2005 17:01:13 -0000, Peter.Hitchman@xxxxxxxxxxx
><Peter.Hitchman@xxxxxxxxxxx> wrote:
>> Hi,
>> From MetaLink:-
>>
>> "dml lock allocation
>> This latch protects the list of State Objects (dml locks). Every time a
>> transaction modifies a table, a DML lock is gotten and released when the
>> change is committed. The number of State Objects for dml locks is
>> determined by
>> the init.ora <Parameter:DML_LOCKS>".
>>
>> So I would be looking at how often you commit.
>> Also what sort of turn over are you getting on the online redo logs? It
>> may well be that they are too small.
>> You may want to investigate having multiple freelists for the table you
>> are inserting into, having many parallel
>> inserts (assuming you have enabled parallel DML), may well be causing a
>> lot of contention for the header block at
>> the start of the segment.
>>
>> Good luck.
>>
>> Pete
>
>----------------------------------------
>eygle from China.
>my site: http://www.eygle.com
>--
>//www.freelists.org/webpage/oracle-l
>
>.
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