local write wait
- From: "Post, Ethan" <Ethan.Post@xxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 7 Jun 2005 12:23:22 -0500
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@xxxxxxxxx>=20
To: chupit@xxxxxxxxx, "oracle-l@xxxxxxxxxxxxx" <oracle-l@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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