近一段时间监控生产数据库的表空间使用情况，发现SYSAUX表空间非常大（17g之多），而且每天都有几十M的增长，看到此现象后，认为这很不正常，分析SYSAUX表空间那些segments占用空间比较大：
SELECT SUM(T.BYTES)/1024/1024 segments_SIZE,T.segment_name
FROM Dba_Segments t WHERE t.tablespace_name='SYSAUX' AND ROWNUM<21 GROUP BY T.segment_name ORDER BY 1 DESC;| segments_size | segment_name |
| 10631.0625 | WRH$_ACTIVE_SESSION_HISTORY |
| 2683.0625 | WRH$_ACTIVE_SESSION_HISTORY_PK |
| 1026.0625 | WRH$_LATCH_MISSES_SUMMARY_PK |
| 730.0625 | WRH$_LATCH_MISSES_SUMMARY |
| 618.0625 | WRH$_SQLSTAT |
| 564.0625 | WRH$_LATCH |
| 496.9375 | WRH$_LATCH_PK |
| 490 | I_WRI$_OPTSTAT_H_OBJ#_ICOL#_ST |
| 471.8125 | WRH$_SYSSTAT_PK |
| 395 | SYS_LOB0000009001C00038$$ |
| 378 | WRI$_OPTSTAT_HISTGRM_HISTORY |
| 371.5 | WRH$_SEG_STAT |
| 370.25 | WRH$_PARAMETER_PK |
| 305.125 | WRH$_SYSSTAT |
| 292.125 | WRH$_PARAMETER |
| 280 | WRH$_SQL_PLAN |
| 274 | WRH$_SYSMETRIC_SUMMARY |
| 268 | SYS_LOB0000008995C00004$$ |
| 257.75 | WRH$_SYSTEM_EVENT_PK |
| 247 | I_WRI$_OPTSTAT_H_ST |
| 233.75 | WRH$_SYSTEM_EVENT |
| 205.4375 | WRH$_SERVICE_STAT_PK |
发现WRH$_ACTIVE_SESSION_HISTORY表以及其索引占据了绝大部分的空间，这个表是oracle 10g 用来存储AWR的相关信息，对应的视图是：dba_hist_active_sess_history 注：oracle提供的dba_hist开头的视图中，都是通过wrh$ 开头的表，wrm$开头的表以及部分dba_hist开头的表关联出来的。
查看快照信息：
SELECT COUNT(*) FROM WRM$_SNAPSHOT;或者SELECT COUNT(*) FROM dba_hist_snapshot;
发现保存有25043个快照！
看看最旧的快照是什么时候的：
SELECT * FROM WRM$_SNAPSHOT t ORDER BY t.snap_id ASC;
发现相关的快照竟是两年前的！
查看此库关于awr的相关参数设置：
SELECT * FROM wrm$_wr_control;或者select a.snap_interval,a.retention,a.topnsql from dba_hist_wr_control a;
| SNAP_INTERVAL | RETENTION | TOPNSQL |
| +00000 01:00:00.0 | +00007 00:00:00.0 | DEFAULT |
保留历史快照的时间是7天，和oracle默认的是一致的，为什么数据库没有删除过期的快照信息？而且还发现所有历史的快照信息并不是连续的，难道这是oracle的bug，还是有人为的删除过历史的快照信息导致了oracle的bug？这个数据库原来是另外一个团队维护的，中间做过一次物理的迁移和升级，在他们手上还做了什么操作呢？一大堆的疑问。
看着sysaux表空间快要满了，只能先想办法先将此表的数据清理写，以降低sysaux表空间的大小。
通过参考metalink文章：WRH$_ACTIVE_SESSION_HISTORY Does Not Get Purged [ID 387914.1]
select table_name,partition_name from dba_tab_partitions where table_name = 'WRH$_ACTIVE_SESSION_HISTORY';
alter session set "_swrf_test_action" = 72;
set serveroutput on declare CURSOR cur_part IS SELECT partition_name from dba_tab_partitions WHERE table_name = 'WRH$_ACTIVE_SESSION_HISTORY'; query1 varchar2(200); query2 varchar2(200); TYPE partrec IS RECORD (snapid number, dbid number); TYPE partlist IS TABLE OF partrec; Outlist partlist; begin dbms_output.put_line('PARTITION NAME SNAP_ID DBID'); dbms_output.put_line('--------------------------- ------- ----------'); for part in cur_part loop query1 := 'select min(snap_id), dbid from sys.WRH$_ACTIVE_SESSION_HISTORY partition ('||part.partition_name||') group by dbid'; execute immediate query1 bulk collect into OutList; if OutList.count > 0 then for i in OutList.first..OutList.last loop dbms_output.put_line(part.partition_name||' Min '||OutList(i).snapid||' '||OutList(i).dbid); end loop; end if; query2 := 'select max(snap_id), dbid from sys.WRH$_ACTIVE_SESSION_HISTORY partition ('||part.partition_name||') group by dbid'; execute immediate query2 bulk collect into OutList; if OutList.count > 0 then for i in OutList.first..OutList.last loop dbms_output.put_line(part.partition_name||' Max '||OutList(i).snapid||' '||OutList(i).dbid); dbms_output.put_line('---'); end loop; end if; end loop; end; / DBMS_WORKLOAD_REPOSITORY.DROP_SNAPSHOT_RANGE( low_snap_id IN NUMBER, high_snap_id IN NUMBER dbid IN NUMBER DEFAULT NULL);
将WRH$_ACTIVE_SESSION_HISTORY的segment占用的大小缩小。