Purging statistics from the SYSAUX tablespace
Whenever statistics in the dictionary are modified, old versions of statistics are saved automatically for future restoring. The old statistics are purged automatically at regular intervals based on the statistics history retention setting and the time of recent statistics gathering performed in the system. Retention is configurable using the ALTER_STATS_HISTORY_RETENTION procedure. The default value is 31 days.
That is normally not too big an issue but in our Peoplesoft environments we run a lot of gather_stats jobs and if the retention period is not managed then the SYSAUX tablespaces can grow very large. In one of our systems the SYSAUX tablespace was 37Gb with over 32Gb consisting of the stats tables and associated indexes. This blog entry will provide the scripts to diagnose and correct excessive tablespace growth due to retained statistics
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | set linesize 120set pagesize 100COLUMN "Item" FORMAT A25COLUMN "Space Used (GB)" FORMAT 999.99COLUMN "Schema" FORMAT A25COLUMN "Move Procedure" FORMAT A40SELECT occupant_name "Item", space_usage_kbytes/1048576 "Space Used (GB)", schema_name "Schema", move_procedure "Move Procedure"FROM v$sysaux_occupantsORDER BY 1/ |
Item Space Used (GB) Schema Move Procedure
------------------------- --------------- ------------------------- ----------------------------------------
AO .00 SYS DBMS_AW.MOVE_AWMETA
EM .08 SYSMAN emd_maintenance.move_em_tblspc
EM_MONITORING_USER .00 DBSNMP
EXPRESSION_FILTER .00 EXFSYS
JOB_SCHEDULER .00 SYS
LOGMNR .01 SYSTEM SYS.DBMS_LOGMNR_D.SET_TABLESPACE
LOGSTDBY .00 SYSTEM SYS.DBMS_LOGSTDBY.SET_TABLESPACE
ODM .00 DMSYS MOVE_ODM
ORDIM .00 ORDSYS
ORDIM/PLUGINS .00 ORDPLUGINS
ORDIM/SQLMM .00 SI_INFORMTN_SCHEMA
SDO .00 MDSYS MDSYS.MOVE_SDO
SM/ADVISOR .02 SYS
SM/AWR .15 SYS
SM/OPTSTAT 11.44 SYS
SM/OTHER .02 SYS
STATSPACK .00 PERFSTAT
STREAMS .00 SYS
TEXT .00 CTXSYS DRI_MOVE_CTXSYS
TSM .00 TSMSYS
ULTRASEARCH .00 WKSYS MOVE_WK
ULTRASEARCH_DEMO_USER .00 WK_TEST MOVE_WK
WM .00 WMSYS DBMS_WM.move_proc
XDB .00 XDB XDB.DBMS_XDB.MOVEXDB_TABLESPACE
XSAMD .00 OLAPSYS DBMS_AMD.Move_OLAP_Catalog
XSOQHIST .00 SYS DBMS_XSOQ.OlapiMoveProc
How long old stats are kept
1 | select dbms_stats.get_stats_history_retention from dual; |
Set retention of old stats to 10 days
1 | exec dbms_stats.alter_stats_history_retention(10); |
Purge stats older than 10 days (best to do this in stages if there is a lot of data (sysdate-30,sydate-25 etc)
1 | exec DBMS_STATS.PURGE_STATS(SYSDATE-10); |
Show available stats that have not been purged
1 | select dbms_stats.get_stats_history_availability from dual; |
Show how big the tables are and rebuild after stats have been purged
1 2 3 4 5 6 7 8 9 | col Mb form 9,999,999col SEGMENT_NAME form a40col SEGMENT_TYPE form a6set lines 120select sum(bytes/1024/1024) Mb, segment_name,segment_type from dba_segmentswhere tablespace_name = 'SYSAUX'and segment_name like 'WRI$_OPTSTAT%'and segment_type='TABLE'group by segment_name,segment_type order by 1 asc |
MB SEGMENT_NAME SEGMEN
---------- ---------------------------------------- ------
0 WRI$_OPTSTAT_OPR TABLE
0 WRI$_OPTSTAT_AUX_HISTORY TABLE
88 WRI$_OPTSTAT_TAB_HISTORY TABLE
126 WRI$_OPTSTAT_IND_HISTORY TABLE
158 WRI$_OPTSTAT_HISTGRM_HISTORY TABLE
4,482 WRI$_OPTSTAT_HISTHEAD_HISTORY TABLE
Show how big the indexes are ready for a rebuild after stats have been purged
1 2 3 4 5 6 7 8 9 10 | col Mb form 9,999,999col SEGMENT_NAME form a40col SEGMENT_TYPE form a6set lines 120select sum(bytes/1024/1024) Mb, segment_name,segment_type from dba_segmentswhere tablespace_name = 'SYSAUX'and segment_name like '%OPT%'and segment_type='INDEX'group by segment_name,segment_type order by 1 asc/ |
MB SEGMENT_NAME SEGMEN
---------- ---------------------------------------- ------
0 WRH$_OPTIMIZER_ENV_PK INDEX
0 I_WRI$_OPTSTAT_OPR_STIME INDEX
0 I_WRI$_OPTSTAT_AUX_ST INDEX
88 I_WRI$_OPTSTAT_TAB_ST INDEX
105 I_WRI$_OPTSTAT_IND_ST INDEX
105 I_WRI$_OPTSTAT_H_ST INDEX
195 I_WRI$_OPTSTAT_TAB_OBJ#_ST INDEX
213 I_WRI$_OPTSTAT_H_OBJ#_ICOL#_ST INDEX
214 I_WRI$_OPTSTAT_IND_OBJ#_ST INDEX
2,055 I_WRI$_OPTSTAT_HH_ST INDEX
3,883 I_WRI$_OPTSTAT_HH_OBJ_ICOL_ST INDEX
Note that you cannot enable row movement and shrink the tables as the indexes are function based
1 2 3 4 5 | alter table WRI$_OPTSTAT_IND_HISTORY enable row movement;alter table WRI$_OPTSTAT_IND_HISTORY shrink space;*ERROR at line 1:ORA-10631: SHRINK clause should not be specified for this object |
1 2 | select 'alter table '||segment_name||' move tablespace SYSAUX;' from dba_segments where tablespace_name = 'SYSAUX'and segment_name like '%OPT%' and segment_type='TABLE' |
Run the rebuild table commands – note that this does cause any gather_stats jobs to fail
alter table WRI$_OPTSTAT_TAB_HISTORY move tablespace sysaux;
alter table WRI$_OPTSTAT_IND_HISTORY move tablespace sysaux;
alter table WRI$_OPTSTAT_HISTHEAD_HISTORY move tablespace sysaux;
alter table WRI$_OPTSTAT_HISTGRM_HISTORY move tablespace sysaux;
alter table WRI$_OPTSTAT_AUX_HISTORY move tablespace sysaux;
alter table WRI$_OPTSTAT_OPR move tablespace sysaux;
alter table WRH$_OPTIMIZER_ENV move tablespace sysaux;
Script to generate rebuild statements
1 2 | select 'alter index '||segment_name||' rebuild online parallel (degree 14);' from dba_segments where tablespace_name = 'SYSAUX'and segment_name like '%OPT%' and segment_type='INDEX' |
Once completed it is best to check that the indexes (indices) are usable
1 2 3 4 5 6 | select di.index_name,di.index_type,di.status from dba_indexes di , dba_tables dtwhere di.tablespace_name = 'SYSAUX'and dt.table_name = di.table_nameand di.table_name like '%OPT%'order by 1 asc/ |
SQL>
INDEX_NAME INDEX_TYPE STATUS
------------------------------ --------------------------- --------
I_WRI$_OPTSTAT_AUX_ST FUNCTION-BASED NORMAL VALID
I_WRI$_OPTSTAT_HH_OBJ_ICOL_ST FUNCTION-BASED NORMAL VALID
I_WRI$_OPTSTAT_HH_ST FUNCTION-BASED NORMAL VALID
I_WRI$_OPTSTAT_H_OBJ#_ICOL#_ST FUNCTION-BASED NORMAL VALID
I_WRI$_OPTSTAT_H_ST FUNCTION-BASED NORMAL VALID
I_WRI$_OPTSTAT_IND_OBJ#_ST FUNCTION-BASED NORMAL VALID
I_WRI$_OPTSTAT_IND_ST FUNCTION-BASED NORMAL VALID
I_WRI$_OPTSTAT_OPR_STIME FUNCTION-BASED NORMAL VALID
I_WRI$_OPTSTAT_TAB_OBJ#_ST FUNCTION-BASED NORMAL VALID
I_WRI$_OPTSTAT_TAB_ST FUNCTION-BASED NORMAL VALID
WRH$_OPTIMIZER_ENV_PK NORMAL VALID
Finally lets see what space has been saved with a retention date of 1 day and a gather schema stats for the SYSASDM schema
1 2 | exec dbms_stats.alter_stats_history_retention(1);select dbms_stats.get_stats_history_retention from dual; |
MB SEGMENT_NAME SEGMEN
---------- ---------------------------------------- ------
0 WRI$_OPTSTAT_OPR TABLE
0 WRI$_OPTSTAT_AUX_HISTORY TABLE
3 WRI$_OPTSTAT_TAB_HISTORY TABLE
4 WRI$_OPTSTAT_IND_HISTORY TABLE
8 WRI$_OPTSTAT_HISTGRM_HISTORY TABLE
104 WRI$_OPTSTAT_HISTHEAD_HISTORY TABLE
MB SEGMENT_NAME SEGMEN
---------- ---------------------------------------- ------
0 WRH$_OPTIMIZER_ENV_PK INDEX
0 I_WRI$_OPTSTAT_OPR_STIME INDEX
0 I_WRI$_OPTSTAT_AUX_ST INDEX
2 I_WRI$_OPTSTAT_IND_ST INDEX
2 I_WRI$_OPTSTAT_TAB_ST INDEX
3 I_WRI$_OPTSTAT_TAB_OBJ#_ST INDEX
4 I_WRI$_OPTSTAT_IND_OBJ#_ST INDEX
5 I_WRI$_OPTSTAT_H_ST INDEX
9 I_WRI$_OPTSTAT_H_OBJ#_ICOL#_ST INDEX
41 I_WRI$_OPTSTAT_HH_ST INDEX
96 I_WRI$_OPTSTAT_HH_OBJ_ICOL_ST INDEX