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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


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
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