突然才發現一個數據庫的LGWR進程的跟蹤文件scm2_lgwr_5690.trc有大量的告警信息，如下所示：
Warning: ;log write time 680ms, size 11569KB
*** ;2015-01-04 02:41:17.122
Warning: ;log write time 520ms, size 2764KB
*** ;2015-01-04 03:11:40.885
Warning: ;log write time 880ms, size 1KB
*** ;2015-01-04 03:24:04.357
Warning: ;log write time 500ms, size 1KB
*** ;2015-01-04 03:29:11.160
Warning: ;log write time 510ms, size 2KB
*** ;2015-01-04 03:30:22.383
Warning: ;log write time 540ms, size 2KB
*** ;2015-01-04 04:04:09.133
Warning: ;log write time 680ms, size 3KB
*** ;2015-01-04 04:15:53.617
Warning: ;log write time 620ms, size 25KB
*** ;2015-01-04 04:20:06.502
Warning: ;log write time 940ms, size 5KB
*** ;2015-01-04 04:31:11.049
Warning: ;log write time 520ms, size 43KB
*** ;2015-01-04 04:32:52.570
Warning: ;log write time 520ms, size 33KB
*** ;2015-01-04 04:33:22.023
Warning: ;log write time 1600ms, size 257KB
*** ;2015-01-04 04:33:22.609
Warning: log write time 590ms, size 443KB
搜索了Metalink上關於該告警的闡述Metalink ID 601316.1,具體內容如下所示（英文部分）：
CHANGES
The problem surfaced after upgrading to 10.2.0.4.
CAUSE
The above warning messages has been introduced in 10.2.0.4 patchset.
The warning message will be generated only if the log write time is more than 500 ms and it will be written to the lgwr trace file.
SOLUTION
These messages are expected in a 10.2.0.4 database in case the log write is more than 500 ms.
This is a warning which means that the write process is not as fast as it intented to be.
So, probably you need to check if the disk is slow or not or for any potential OS causes.
If everything looks fine at the hardware level or OS level i.e if enviroment is unable to deliver a faster service because of its own nature,then you can ignore this message.then you can safely ignore these messages. The trace file can easily be deleted or truncated.
Also, according to Bug:7559549 , these trace can be disabled by setting event 10468 level 4.
剛好我們數據庫版本也是10.2.0.4.0，於是我檢查了另外其它幾台數據庫，發現基本上都有這類錯誤，根據官方文檔，如果磁盤沒有什麼問題，可以忽略這個告警信息。另外我也在兩位大師Eygle&惜分飛博客裡面發現了對這個告警現象的記錄、描述.應該可以忽略這個告警。另外，也可以通過下面命令取消該trace命令，如下所示：
ALTER SYSTEM SET EVENTS '10468 trace name context off';
參考資料：
http://www.eygle.com/archives/2009/11/log_write_time.html
http://www.xifenfei.com/1563.html
