log file sync排查方向

1.频繁commit或者rollback

无伴生

AWR看Key Instance Activity Stats

该图表示，总提交123w次，平均每秒339次

2.IO缓慢

伴生log file parallel write等待事件

可能是io紧张，导致lgwr写的慢，也可以去看lgwr的trc日志，20ms以下是正常的

根据snap_id分时间，测io的平均、峰值、等待。看峰值

SELECT

TO_CHAR(s.END_INTERVAL_TIME, 'YYYY-MM-DD HH24:MI') AS end_time,

s.instance_number,

ms.metric_name,

ROUND(ms.average, 2) AS avg_value,

ROUND(ms.maxval, 2) AS max_value,

ROUND(ms.minval, 2) AS min_value

FROM

dba_hist_sysmetric_summary ms,

dba_hist_snapshot s

WHERE

ms.snap_id = s.snap_id

AND ms.dbid = s.dbid

AND ms.instance_number = s.instance_number

AND ms.metric_name IN ('Physical Read Total IO Requests Per Sec', 'Physical Write Total IO Requests Per Sec', 'Physical Read Total Bytes Per Sec', 'Physical Write Total Bytes Per Sec')

AND s.END_INTERVAL_TIME BETWEEN TO_DATE('2025-03-01 00:00:00', 'YYYY-MM-DD HH24:MI:SS') AND TO_DATE('2025-03-31 23:59:59', 'YYYY-MM-DD HH24:MI:SS')

ORDER BY

s.END_INTERVAL_TIME;

3.过大的日志缓冲区(Log Buffer)

4.CPU负载高。

无伴生

5.RAC私有网络性能差,导致LMS同步commit SCN慢

伴生gc等待事件

6.控制文件争用

（rman频繁、asm控制文件的具体磁盘io满、v$视图频繁、控制文件过大）

伴生control file sequential read

AWR看IOStat by Filetype summary

7.bug（11203）(Doc ID 13074706.8)