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Home -> Community -> Mailing Lists -> Oracle-L -> Re: what's mean of "enqueue hash chains" latch?
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_at_thomson.com
<Peter.Hitchman_at_thomson.com> 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
-- http://www.freelists.org/webpage/oracle-lReceived on Sat Jan 08 2005 - 21:04:18 CST
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