4、演示索引监控

　　a、单个索引监控

-->演示环境
scott@CNMMBO> select * from v$version where rownum<2;

BANNER
----------------------------------------------------------------
Oracle Database 10g Release 10.2.0.3.0 - 64bit Production

-->创建测试表
scott@CNMMBO> create table tb_emp as select * from emp;

-->为测试表创建索引
scott@CNMMBO> create index i_tb_emp_empno on tb_emp(empno);

-->收集统计信息
scott@CNMMBO> exec dbms_stats.gather_table_stats('SCOTT'，'TB_EMP'，cascade=>true);

-->查看索引信息
scott@CNMMBO> @idx_info
Enter value for owner: scott
Enter value for table_name: tb_emp

Table Name                INDEX_NAME                     CL_NAM               CL_POS STATUS   IDX_TYP         DSCD
------------------------- ------------------------------ -------------------- ------ -------- --------------- ----
TB_EMP                    I_TB_EMP_EMPNO                 EMPNO                     1 VALID    NORMAL          ASC

-->查看索引使用情况
-->此时use列为NO，表明索引未被使用到
scott@CNMMBO> @idx_usage_tb            
Enter value for 1: tb_emp
Enter value for 2: all
Enter value for 2: all

Table Name                INDEX_NAME                     USE START_MONITORING    END_MONITORING
------------------------- ------------------------------ --- ------------------- -------------------
TB_EMP                    I_TB_EMP_EMPNO                 NO  03/19/2013 17:43:49

-->实施即席查询
scott@CNMMBO> select empno，ename，job from tb_emp where empno=7788;

     EMPNO ENAME      JOB
---------- ---------- ---------
      7788 SCOTT      ANALYST

-->再次查看时USE列已经为YES
scott@CNMMBO> @idx_usage_tb
Enter value for 1: tb_emp
Enter value for 2: all
Enter value for 2: all

Table Name                INDEX_NAME                     USE START_MONITORING    END_MONITORING
------------------------- ------------------------------ --- ------------------- -------------------
TB_EMP                    I_TB_EMP_EMPNO                 YES 03/19/2013 17:43:49

-->禁用索引监控
scott@CNMMBO> alter index I_TB_EMP_EMPNO nomonitoring usage;

Index altered.

　　b、schema级别的索引监控

-->切换到另外一个数据库cnbo1
scott@CNMMBO> conn goex_admin/xxxxx@cnbo1
Connected.

-->下面的查询表明没有表开启索引监控
goex_admin@CNBO1> @idx_usage;

no rows selected

-->开启索引监控
goex_admin@CNBO1> @idx_monitor_on

INDEX_NAME                     MON USE START_MONITORING    END_MONITORING
------------------------------ --- --- ------------------- -------------------
PK_AAH                         YES NO  03/19/2013 17:48:32
IDX_GOAAE1                     YES NO  03/19/2013 17:48:32
PK_GOAAT                       YES NO  03/19/2013 17:48:32
PK_GOAACTL                     YES NO  03/19/2013 17:48:32
.......                            ................

-->关闭索引监控
goex_admin@CNBO1> @idx_monitor_off
INDEX_NAME                     MON USE START_MONITORING    END_MONITORING
------------------------------ --- --- ------------------- -------------------
PK_GOARL                       NO  NO  03/19/2013 17:48:30 03/19/2013 17:50:02
IDX_GOAQU1                     NO  NO  03/19/2013 17:48:30 03/19/2013 17:50:02
IDX_GOAQU2                     NO  NO  03/19/2013 17:48:30 03/19/2013 17:50:02

-->连接到原来的db，查看曾经开启索引监控的使用情况
goex_admin@CNBO1> conn scott/tiger@cnmmbo

Connected.

goex_admin@CNMMBO> @idx_usage
Enter value for input_owner: GOEX_ADMIN
Enter value for input_owner: GOEX_ADMIN

OWNER           INDEX_NAME                     Table Name                MON USE START_MONITORING    END_MONITORING
--------------- ------------------------------ ------------------------- --- --- ------------------- ----------------
SCOTT           I_TB_EMP_EMPNO                 TB_EMP                    NO  YES 03/19/2013 17:43:49 03/19/2013 17:46:04
GOEX_ADMIN      ACC_GRP_EXT_INFO_TBL_LOG_PK    ACC_GRP_EXT_INFO_TBL_LOG  YES YES 02/22/2013 15:58:42
GOEX_ADMIN      IDX_TDCL_CONTRACT_NUM          TRADE_CLIENT_TBL          YES YES 02/22/2013 15:58:42
GOEX_ADMIN      IDX_TDCL_SETTLED_DATE          TRADE_CLIENT_TBL          YES YES 02/22/2013 15:58:42
GOEX_ADMIN      IDX_TDCL_ACC_NUM               TRADE_CLIENT_TBL          YES YES 02/22/2013 15:58:41
GOEX_ADMIN      IDX_TDCL_INSTRU_ID             TRADE_CLIENT_TBL          YES YES 02/22/2013 15:58:42

　　5、索引监控的建议与弊端

　　a、选择数据库高峰期实施索引监控，以及尽可能使用较长的监控周期来判断索引是否被使用

　　b、可以对特定时间段实施多次监控以判断索引的使用频率（初略值）

　　c、索引监控在一定程度上耗用系统资源，一旦监控完毕后应即时关闭以避免其带来的额外开销

　　d、索引监控仅仅从索引的使用与否来描述索引使用，并未提供详细的索引使用频率，b点提到的方法也只是初略值