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较少见的等待事件Local Write Wait-- Event 60

原创 Linux操作系统 作者:v_fantasy 时间:2009-04-15 14:04:10 0 删除 编辑

Oracle 10.2.0.1.0
在开发环境里面truncate一些列表,速度奇慢。看了一下session等待事件 Local Write Wait- Event# 是60,Class是 User I/O。

上Metalink也没有查到这个等待事件,Google了一下,还是找到了一点解释。



Re: local write wait event

    * From: K Gopalakrishnan
    * To: chupit@xxxxxxxxx, "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.

 

During TRUNCATEs the session has to a
local checkpoint and during this process, the session may wait for
'local write' wait.

果然有local checkpoint

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