gcs log flush sync --wait event
在客户处AWR报告中发现TOP 5 EVENT出出现如下等待事件：
|
Event |
Waits |
Time(s) |
Avg Wait(ms) |
% Total Call Time |
Wait Class |
|
CPU time |
|
4,989 |
|
96.6 |
|
|
gcs log flush sync |
129,223 |
3,103 |
24 |
60.1 |
Other |
|
reliable message |
295 |
33 |
111 |
.6 |
Other |
|
gc cr block busy |
764 |
16 |
21 |
.3 |
Cluster |
|
log file sync |
10,132 |
8 |
1 |
.2 |
Commit |
This is how it happens -
1)You fired an update statement on Instance-2.
2)However, the request for desired blocks was gone to Instance-1. So Instance-2 was
waiting on ''gc cr request'.
3)Instance-1 had the requested blocks but before it ships the blocks to Instance-2, it need to flush the changes from current block
to redo logs on disks. Until this is done Instance-2 waits on event - 'gcs log flush sync'.
The cause of this wait event 'gcs log flush sync' is mainly - Redo log IO performance.
To avoid this problem you need to =
1)Improve the Redo log I/o performance.
2) Set undersore parameter "_cr_server_log_flush" =false
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