Local write wait

Oracle: local write wait

Happens when

Truncating a table

Wait for Data Cache to be cleared of all blocks of truncated table

Wait by shadow for DBWR

"Truncate causes the dirty buffers to be flushed to disk. Metalink note 334822.1 explains the process." Michael McMullen

If a problem try

GTT (global temporary tables)

or

Reduce fast_start_mttr_targe

http://www.freelists.org/post/oradebug/local-write-wait-event,15

Re: local write wait event

From: K Gopalakrishnan <kaygopal@xxxxxxxxx>

To: chupit@xxxxxxxxx, "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>

Date: Mon, 18 Oct 2004 11:42:45 -0700 (PDT)

Edgar,

Sorry for the delay in my reply. I was traveling and was in Beirut for a week and just returned to Bangalore. You have got some valuable advice (esp the one from Jonathan).

Basically 'local write' wait happens (as the name indicates) when the session is waiting for its local (means writes pending because of its own operation) write operation. This could happen typically if the underlying disc has some serious problems (one of the member disk crash in RAID-05 - for example, or a controller failure). That is why I might have said ' you never see this wait in the normal databases!'. You may see this during (rarely) Truncating a large table while most of the buffers of that table in cache. During TRUNCATEs the session has to a local checkpoint and during this process, the session may wait for 'local write' wait.

We have not documented this in 'Oracle Wait Interface' as it is very uncommon. May be we can think of adding similar events in the Misc Waits in next edition.