突然才发现一个数据库的LGWR进程的跟踪文件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上关于该告警的阐述Metalink ID 601316.1,具体内容如下所示（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.
刚好我们数据库版本也是10.2.0.4.0，于是我检查了另外其它几台数据库，发现基本上都有这类错误，根据官方文档，如果磁盘没有什么问题，可以忽略这个告警信息。另外我也在两位大师Eygle&惜分飞博客里面发现了对这个告警现象的记录、描述.应该可以忽略这个告警。另外，也可以通过下面命令取消该trace命令，如下所示：
ALTER SYSTEM SET EVENTS ‘10468 trace name context off‘;
参考资料：
http://www.eygle.com/archives/2009/11/log_write_time.html
http://www.xifenfei.com/1563.html