遇到latch: row cache objects等待事件

遇到latch: row cache objects等待事件:

前台业务说很慢,于是检查等待事件:

参考文档:

WAITEVENT: "latch: row cache objects" Reference Note (文档 ID 1550722.1)

SQL> select inst_id,event,count(1) from gv$session where wait_class#<> 6 group by inst_id,event order by 1,3;

INST_ID EVENT                                                              COUNT(1)
---------- ---------------------------------------------------------------- ----------
1 control file parallel write                                               1
1 SQL*Net message to client                                                 1
1 reliable message                                                          1
1 direct path read                                                          2
1 Standby redo I/O                                                          2
1 latch: row cache objects                                                164

SQL>

SQL> select count(*),P1RAW from v$session where event = 'latch: row cache objects' group by P1RAW;

COUNT(*) P1RAW
---------- ----------------
122 0000000E364A3470

SQL>     SELECT
2          kqrsttxt PARAMETER,
3     -- kqrstcid CACHE#,
4          kqrstcln "Lchild#",
5          kqrstgrq "DCGets",
6          l.gets   "LGets",
7          l.misses "Misses"
8    FROM X$KQRST, V$LATCH_CHILDREN l
9   WHERE l.addr='&P1RAW'
10     and l.child#=KQRSTCLN
11   ORDER BY 1,2
12   ;
Enter value for p1raw: 0000000E364A3470
old   9:  WHERE l.addr='&P1RAW'
new   9:  WHERE l.addr='0000000E364A3470'

PARAMETER                           Lchild#     DCGets      LGets     Misses
-------------------------------- ---------- ---------- ---------- ----------
dc_rollback_segments                      1  986621136 2959867775 1557382997

SQL>

SQL> select * from V$LATCHHOLDER;

PID        SID LADDR            NAME                       GETS
---------- ---------- ---------------- -------------------- ----------
292        300 0000000E364A3470 row cache objects    3130388543

然后去查询sid=300的session,没有查到:

select sid,serial#,status,state,event,machine,program from v$session where sid=300;

然后再去查询等待事件: select inst_id,event,count(1) from gv$session where wait_class#<> 6 group by inst_id,event order by 1,3;

发现已经没有latch: row cache objects 这个等待事件了...

估计sid=300的session退出了.