local write wait

Googles local write wait and came up with this old message. I am doing a 20,000,000 row insert append and I am seeing this as the top wait. I believe there might be some IO issues, namely everything going through one controller. When I watch the disks usins "statit | http://www.solarisinternals.com/si/downloads/index.php" it shows the disk all around 30%, my guess is the controller is saturated. I can't tell from the email below if this wait event signifies a real problem like a malfunction or defect in the IO subsystem, or just a bottleneck on the controller?

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Re: local write wait event
From: K Gopalakrishnan <kaygopal_at_xxxxxxxxx>=20 To: chupit_at_xxxxxxxxx, "oracle-l_at_xxxxxxxxxxxxx" <oracle-l_at_xxxxxxxxxxxxx>=20 Date: Mon, 18 Oct 2004 11:42:45 -0700 (PDT)=20 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).=20

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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