1.现象:
客户10.2.0.4 RAC环境，出现大量的library cache lock和cursor: pin S wait on X等待，经分析是由于统计信息收集僵死导致的。
数据库在8点到9点期间，数据库两个节点都存在明显的cursor: pin S wait on X和library cache lock的等待：
TOP 5 EVENT:
|
Event |
Waits |
Time(s) |
Avg Wait(ms) |
% Total Call Time |
Wait Class |
|
cursor: pin S wait on X |
1,573,056 |
30,651 |
19 |
146.2 |
Concurrency |
|
library cache lock |
31,757 |
7,009 |
221 |
33.4 |
Concurrency |
|
CPU time |
6,416 |
30.6 |
|||
|
DFS lock handle |
12,381 |
2,979 |
241 |
14.2 |
Other |
|
latch: library cache |
1,646 |
1,974 |
1,199 |
9.4 |
Concurrency |
|
Event |
Waits |
Time(s) |
Avg Wait(ms) |
% Total Call Time |
Wait Class |
|
cursor: pin S wait on X |
17,586,451 |
342,437 |
19 |
812.1 |
Concurrency |
|
library cache lock |
63,657 |
30,153 |
474 |
71.5 |
Concurrency |
|
CPU time |
3,820 |
9.1 |
|||
|
db file sequential read |
241,761 |
1,094 |
5 |
2.6 |
User I/O |
|
inactive session |
两个节点的等待现象基本一致，而节点1上还存在明显的DFS lock handle等待事件。
通过分析ASH信息，发现library cache lock和cursor: pin S wait on X等待基本上都是6点之后才开始出现：
2.分析原因
SELECT trunc(sample_time, 'hh24') TIME, COUNT(*) FROM WRH$_ACTIVE_SESSION_HISTORY ash, wrh$_event_name en WHERE ash.event_id = en.event_id AND sample_time>= to_timestamp('20130703', 'yyyymmdd') AND event_name IN ('cursor: pin S wait on X', 'library cache lock') GROUP BY trunc(sample_time, 'hh24') ORDER BY 1;