oracle监控索引是否使用

如果你打开监控索引的情况下，通过v$object_usage视图可以知道索引是否使用,这为我们删除多余的索引很有帮助
SQL> desc v$object_usage;
Name                                      Null?    Type
----------------------------------------- -------- ----------------------------
INDEX_NAME                                NOT NULL VARCHAR2(30)
TABLE_NAME                                NOT NULL VARCHAR2(30)
MONITORING                                         VARCHAR2(3)
USED                                               VARCHAR2(3)
START_MONITORING                                   VARCHAR2(19)
END_MONITORING                                     VARCHAR2(19)

--打开索引监控
SQL> alter index idx_test_oid monitoring usage;

Index altered.

--可以看在此视图中有一条记录，但use字段显示为no,表示此索引还未使用
SQL> select * from v$object_usage;

INDEX_NAME                     TABLE_NAME                     MON USE START_MONITORING    END_MONITORING
------------------------------ ------------------------------ --- --- ------------------- ----------
IDX_TEST_OID                   TEST                           YES NO  05/06/2007 20:35:56

SQL>
SQL>
--使用索引
SQL> select * from test where object_id=1;

no rows selected

--这时我们看到use字段已变成YES,表时此索引自监控以来，被使用过，但使用的次数不知道。
SQL> select * from v$object_usage;

INDEX_NAME                     TABLE_NAME                     MON USE START_MONITORING    END_MONITORING
------------------------------ ------------------------------ --- --- ------------------- ----------
IDX_TEST_OID                   TEST                           YES YES 05/06/2007 20:35:56

SQL>
SQL>
--使用以下语法停止索引监控
SQL> alter index idx_test_oid nomonitoring usage;

Index altered.

SQL> select * from v$object_usage;

INDEX_NAME                     TABLE_NAME                     MON USE START_MONITORING    END_MONITORING
------------------------------ ------------------------------ --- --- ------------------- ----------
IDX_TEST_OID                   TEST                           NO  YES 05/06/2007 20:35:56 05/06/2007 20:40:35

--那我们如何删除这些监控记录了
SQL> delete from object_usage;
delete from object_usage
*
ERROR at line 1:
ORA-00942: table or view does not exist

--这个视图建立在sys用户下的object_usage 上
SQL> conn sys/sys as sysdba
Connected.
SQL> delete from object_usage;

1 row deleted.

SQL> commit;

Commit complete.

--我们再次查询，发现没有记录了
SQL> conn test/test
Connected.
SQL> select * from v$object_usage;

no rows selected