- Oracle索引监控(monitor index)合理的为数据库表上创建战略性索引,可以极大程度的提高了查询性能。但事实上日常中我们所创建的索引并非战略性索引,恰恰是大量冗余或是根本没有用到的索引耗用了大量的存储空间,导致DML性能低下。Oracle/" target=_blank>Oracle 提供了索引监控特性来初略判断未使用到的索引。本文描述如何使用Oracle 索引的监控。1、冗余索引的弊端大量冗余和无用的索引导致整个数据库性能低下,耗用了大量的CPU与I/O开销,具体表现如下:a、耗用大量的存储空间(索引段的维护与管理)b、增加了DML完成的时间c、耗用大量统计信息(索引)收集的时间d、结构性验证时间f、增加了恢复所需的时间2、单个索引监控a、对于单个索引的监控,可以使用下面的命令来完成alter index <INDEX_NAME> monitoring usage;b、关闭索引监控alter index <INDEX_NAME> nomonitoring usage;c、观察监控结果(查询v$object_usage视图)select * from v$object_usage3、schema级别索引监控(不含SYS用户)[sql]a、直接执行脚本来开启索引监控robin@SZDB:~/dba_scripts/custom/sql> more idx_monitor_on.sqlSET HEADING OFF FEEDBACK OFF TERMOUT OFF ECHO OFF;SET PAGESIZE 0;SPOOL /tmp/mnt_idx.sqlSELECT 'ALTER INDEX ' || owner || '.' || index_name || ' MONITORING USAGE;'FROM dba_indexesWHERE owner IN (SELECT usernameFROM dba_usersWHERE account_status = 'OPEN')AND owner NOT IN ('SYS', 'SYSTEM', 'PERFSTAT', 'MGMT_VIEW', 'MONITOR', 'SYSMAN', 'DBSNMP');SPOOL OFF;@/tmp/mnt_idx.sql;SET HEADING ON FEEDBACK ON TERMOUT ON;SET PAGESIZE 80;SELECT index_name,monitoring,used,start_monitoring,end_monitoringFROM v$object_usage;ho rm -rf /tmp/mnt_idx.sqlb、禁用索引监控robin@SZDB:~/dba_scripts/custom/sql> more idx_monitor_off.sqlSET HEADING OFF FEEDBACK OFF TERMOUT OFF ECHO OFF;SET PAGESIZE 0;SPOOL /tmp/un_mnt_idx.sqlSELECT 'ALTER INDEX ' || owner || '.' || index_name || ' NOMONITORING USAGE;'FROM dba_indexesWHERE owner IN (SELECT usernameFROM dba_usersWHERE account_status = 'OPEN')AND owner NOT IN ('SYS', 'SYSTEM', 'PERFSTAT', 'MGMT_VIEW', 'MONITOR', 'SYSMAN', 'DBSNMP');SPOOL OFF;@/tmp/un_mnt_idx.sql;SET HEADING ON FEEDBACK ON TERMOUT ON;SET PAGESIZE 80;--> Author : Robinson--> Blog : http://blog.csdn.net/robinson_0612SELECT index_name,monitoring,used,start_monitoring,end_monitoringFROM v$object_usage;ho rm -rf /tmp/un_mnt_idx.sqlc、查看索引监控结果set linesize 190SELECT u.name owner,io.name index_name,t.name table_name,DECODE (BITAND (i.flags, 65536), 0, 'NO', 'YES') monitoring,DECODE (BITAND (ou.flags, 1), 0, 'NO', 'YES') used,ou.start_monitoring start_monitoring,ou.end_monitoring end_monitoringFROM sys.user$ u,sys.obj$ io,sys.obj$ t,sys.ind$ i,sys.object_usage ouWHERE i.obj# = ou.obj# AND io.obj# = ou.obj# AND t.obj# = i.bo# AND u.user# = io.owner#AND u.name=decode(upper('&input_owner'),'ALL',u.name,upper('&input_owner'));4、演示索引监控[sql]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_infoEnter value for owner: scottEnter value for table_name: tb_empTable 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_tbEnter value for 1: tb_empEnter value for 2: allEnter value for 2: allTable 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YESscott@CNMMBO> @idx_usage_tbEnter value for 1: tb_empEnter value for 2: allEnter value for 2: allTable 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cnbo1scott@CNMMBO> conn goex_admin/xxxxx@cnbo1Connected.-->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_onINDEX_NAME MON USE START_MONITORING END_MONITORING------------------------------ --- --- ------------------- -------------------PK_AAH YES NO 03/19/2013 17:48:32IDX_GOAAE1 YES NO 03/19/2013 17:48:32PK_GOAAT YES NO 03/19/2013 17:48:32PK_GOAACTL YES NO 03/19/2013 17:48:32....... ................-->关闭索引监控goex_admin@CNBO1> @idx_monitor_offINDEX_NAME MON USE START_MONITORING END_MONITORING------------------------------ --- --- ------------------- -------------------PK_GOARL NO NO 03/19/2013 17:48:30 03/19/2013 17:50:02IDX_GOAQU1 NO NO 03/19/2013 17:48:30 03/19/2013 17:50:02IDX_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@cnmmboConnected.goex_admin@CNMMBO> @idx_usageEnter value for input_owner: GOEX_ADMINEnter value for input_owner: GOEX_ADMINOWNER 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 17:46:04GOEX_ADMIN ACC_GRP_EXT_INFO_TBL_LOG_PK ACC_GRP_EXT_INFO_TBL_LOG YES YES 02/22/2013 15:58:42GOEX_ADMIN IDX_TDCL_CONTRACT_NUM TRADE_CLIENT_TBL YES YES 02/22/2013 15:58:42GOEX_ADMIN IDX_TDCL_SETTLED_DATE TRADE_CLIENT_TBL YES YES 02/22/2013 15:58:42GOEX_ADMIN IDX_TDCL_ACC_NUM TRADE_CLIENT_TBL YES YES 02/22/2013 15:58:41GOEX_ADMIN IDX_TDCL_INSTRU_ID TRADE_CLIENT_TBL YES YES 02/22/2013 15:58:425、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