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 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_usage

3、schema级别索引监控(不含SYS用户)

a、直接执行脚本来开启索引监控
robin@SZDB:~/dba_scripts/custom/sql> more idx_monitor_on.sql
SET HEADING OFF  FEEDBACK OFF  TERMOUT OFF  ECHO OFF;
SET PAGESIZE 0;
SPOOL /tmp/mnt_idx.sql

SELECT 'ALTER INDEX ' || owner || '.' || index_name || ' MONITORING USAGE;'
  FROM dba_indexes
  WHERE owner IN (SELECT username
                  FROM dba_users
                  WHERE 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_monitoring
  FROM v$object_usage;

ho rm -rf /tmp/mnt_idx.sql

b、禁用索引监控
robin@SZDB:~/dba_scripts/custom/sql> more idx_monitor_off.sql
SET HEADING OFF  FEEDBACK OFF  TERMOUT OFF  ECHO OFF;
SET PAGESIZE 0;
SPOOL /tmp/un_mnt_idx.sql
SELECT 'ALTER INDEX ' || owner || '.' || index_name || ' NOMONITORING USAGE;'
  FROM dba_indexes
  WHERE owner IN (SELECT username
                  FROM dba_users
                  WHERE 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-0612

SELECT index_name,
      monitoring,
      used,
      start_monitoring,
      end_monitoring
  FROM v$object_usage;

ho rm -rf /tmp/un_mnt_idx.sql

c、查看索引监控结果
set linesize 190
SELECT 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_monitoring
  FROM sys.user$ u,
      sys.obj$ io,
      sys.obj$ t,
      sys.ind$ i,
      sys.object_usage ou
 WHERE 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'));

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