填充操作做10046 level 12 trace

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注意col_usage$的数据同*_tab_modifications类似，

从查询到数据刷新到col_usage$存在一段时间的延迟，

所以我们立即查询col_usage$将得不到任何记录，

可以手动执行DBMS_STATS.FLUSH_DATABASE_MONITORING_INFO将缓存中的信息刷新到字典上

 

SQL> select * from col_usage$ where obj#=1323013;

no rows selected

 

SQL> oradebug setmypid;

Statement processed.

 

针对FLUSH_DATABASE_MONITORING_INFO填充操作做10046 level 12 trace

 

SQL> oradebug event 10046 trace name context forever,level 12;

Statement processed.

 

 

 

SQL> exec DBMS_STATS.FLUSH_DATABASE_MONITORING_INFO;

PL/SQL procedure successfully completed.

 

SQL> select * from col_usage$ where obj#=1323013;

 

      OBJ#    INTCOL# EQUALITY_PREDS EQUIJOIN_PREDS NONEQUIJOIN_PREDS RANGE_PREDS LIKE_PREDS NULL_PREDS TIMESTAMP

---------- ---------- -------------- -------------- ----------------- ----------- ---------- ---------- ---------

   1323013          1              1              0                 0           0          0          0 19-AUG-11

 

=============10046 trace content====================

 

lock table sys.col_usage$ in exclusive mode nowait

 

在测试中可以发现10.2.0.4上DBMS_STATS.FLUSH_DATABASE_MONITORING_INFO存储过程会优先使用

lock in exclusive mode nowait来锁住col_usage$基表，

如果lock失败则会反复尝试1100次，

若仍不能锁住col_usage$表则放弃更新col_usage$上的数据，避免造成锁等待和死锁。

 

 

Cksxm.c

Monitor Modification Hash Table Base

modification hash table entry

modification hash table chunk

monitoring column usage element

ksxmlock_1

lock table sys.col_usage$ in exclusive mode

lock table sys.col_usage$ in exclusive mode nowait

 

update sys.col_usage$

   set equality_preds    = equality_preds +

                           decode(bitand(:flag, 1), 0, 0, 1),

       equijoin_preds    = equijoin_preds +

                           decode(bitand(:flag, 2), 0, 0, 1),

       nonequijoin_preds = nonequijoin_preds +

                           decode(bitand(:flag, 4), 0, 0, 1),

       range_preds       = range_preds + decode(bitand(:flag, 8), 0, 0, 1),

       like_preds        = like_preds + decode(bitand(:flag, 16), 0, 0, 1),

       null_preds        = null_preds + decode(bitand(:flag, 32), 0, 0, 1),

       timestamp         = :time

 where obj# = :ob jn

   and intcol# = :coln

 

insert into sys.col_usage$

  (obj#,

   intcol#,

   equality_preds,

   equijoin_preds,

   nonequijoin_preds,

   range_preds,

   like_preds,

   null_preds,

   timestamp)

values

  (:objn,

   :coln,

   decode(bitand(:flag, 1), 0, 0, 1),

   decode(bitand(:flag, 2), 0, 0, 1),

   decode(bitand(:flag, 4), 0, 0, 1),

   decode(bitand(:flag, 8), 0, 0, 1),

   decode(bitand(:flag, 16), 0, 0, 1),

   decode(bitand(:flag, 32), 0, 0, 1),

   :time)