人工模拟获取latch

人工模拟获取latch



任意地dump一latches结构文件:

SQL> oradebug dump latches 10

ORA-00074: no process has been specified

SQL> oradebug setmypid

Statement processed.

SQL> oradebug dump latches 10

Statement processed.

SQL> oradebug tracefile_name

/oracle/diag/rdbms/orcl/orcl/trace/orcl_ora_5564.trc



找到文件并随便找一个latch地址查看：

我们这里找的是地址为0x60019d98的一个active checkpoint queue，当前状态为free：

60019d98  active checkpoint queue latch level=5

        Location from where latch is held: kcbk.h LINE:2222 ID:kcbbacq: scan active checkpoints:


        Context saved from call: 0

        state=free [value=0] wlstate=free [value=0]

    gotten 2345 times wait, failed first 0 sleeps 0

    gotten 0 times nowait, failed: 0



通过oradebug验证：

SQL> oradebug peek 0x60019d98 8

[060019D98, 060019DA0) = 00000000 00000000   

该latch的当前值为0，确为free状态，我将它值改动为1：

SQL> oradebug poke 0x60019d98 2 1

BEFORE: [060019D98, 060019D9C) = 00000000

AFTER:  [060019D98, 060019D9C) = 00000001

再次dump一个latches结构文件，并找到上述latch的信息：

60019d98  active checkpoint queue latch level=5

        Location from where latch is held: kcbk.h LINE:2222 ID:kcbbacq: scan active checkpoints:

        Context saved from call: 0

        state=busy [holder orapid=1] wlstate=free [value=0]

    waiters [orapid (seconds since: put on list, posted, alive check)]:

     10 (30, 1402142587, 30)

     waiter count=1

    gotten 2607 times wait, failed first 0 sleeps 0

    gotten 0 times nowait, failed: 0

的状态busy。

版权声明：本文博主原创文章，博客，未经同意不得转载。