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DROP_SNAPSHOT_RANGE过程不能清理表RM$_SNAPSHOT_DETAILS

2016-06-30 23:11 435 查看
今天在测试、验证DROP_SNAPSHOT_RANGE不能彻底快照的过程中遇到了DROP_SNAPSHOT_RANGE无法清理WRM$_SNAPSHOT_DETAILS表中数据的情况，测试服务器版本为10.2.0.5.0，AWR的快照是1小时采集一次数据，快照保留14天，也就是二周。具体情况如下所示：

SQL>select*fromv$version;
BANNER
----------------------------------------------------------------
OracleDatabase10gRelease10.2.0.5.0-64bitProduction
PL/SQLRelease10.2.0.5.0-Production
CORE10.2.0.5.0Production
TNSforLinux:Version10.2.0.5.0-Production
NLSRTLVersion10.2.0.5.0-Production
SQL>COLSNAP_INTERVALFORA20;
SQL>COLTETENTIONFORA26;
SQL>SELECT*FROMdba_hist_wr_control;
DBIDSNAP_INTERVALRETENTIONTOPNSQL
-------------------------------------------------------------------
3990839260+0000001:00:00.0+0001400:00:00.0DEFAULT
SQL>SELECTMIN(SNAP_ID),MAX(SNAP_ID)FROMdba_hist_snapshot;
MIN(SNAP_ID)MAX(SNAP_ID)
------------------------
741759195
SQL>





SQL>SELECTMIN(SNAP_ID),MAX(SNAP_ID)FROMdba_hist_snapshot;
MIN(SNAP_ID)MAX(SNAP_ID)
------------------------
741759196
SQL>selectdbid,status,count(*)
2fromwrm$_snapshot
3groupbydbid,status;
DBIDSTATUSCOUNT(*)
------------------------------
399083926001250
SQL>selectmin(snap_id),max(snap_id),dbidfromwrm$_snapshot
2groupbydbid;
MIN(SNAP_ID)MAX(SNAP_ID)DBID
----------------------------------
7417591963990839260
SQL>execdbms_workload_repository.drop_snapshot_range(7417,59196,3990839260);
PL/SQLproceduresuccessfullycompleted.
SQL>selectmin(snap_id),max(snap_id),dbidfromwrm$_snapshot
2groupbydbid;
MIN(SNAP_ID)MAX(SNAP_ID)DBID
----------------------------------
7417591973990839260
SQL>selectmin(snap_id),max(snap_id),dbidfromwrm$_snapshot
2groupbydbid;
MIN(SNAP_ID)MAX(SNAP_ID)DBID
----------------------------------
7417591973990839260
SQL>SELECTMIN(SNAP_ID),MAX(SNAP_ID)FROMdba_hist_snapshot;
MIN(SNAP_ID)MAX(SNAP_ID)
------------------------
741759197




如上实验所示，DROP_SNAPSHOT_RANGE不能清理WRM$_SNAPSHOT_DETAILS中的数据，当然对于的空间就不会释放，另外，有些版本中Oracle仅仅修改了对应SNAPSHOT的状态，而并没有删除快照。PS:有些人可能被上面又是DBA_HIST_SNAPSHOT，又是WRM$_SNAPSHOT_DETAILS弄得有点晕，其实DBA_HIST_SNAPSHOT是视图,它的数据来源于表WRM$_SNAPSHOT_DETAILS，使用下面SQL就能查看具体定义
SELECTOWNER,VIEW_NAME,TEXTFROMDBA_VIEWSWHEREVIEW_NAME='DBA_HIST_SNAPSHOT';

"selectsnap_id,dbid,instance_number,startup_time,
begin_interval_time,end_interval_time,
flush_elapsed,snap_level,error_count
fromWRM$_SNAPSHOT
wherestatus=0"

其实这个是一个Bug引起的，官方文档WRM$_SNAPSHOT_DETAILSTableisNotPurged(文档ID1489801.1)和文档Document9797851.8Bug9797851-WRM$_SNAPHOST_DETAILSisneverpurged都有描述这个Bug

APPLIESTO:
OracleDatabase-EnterpriseEdition-Version11.2.0.3to12.1.0.1[Release11.2to12.1]
Informationinthisdocumentappliestoanyplatform.

SYMPTOMS
Thefollowingsymptomsareobserved:

AWRpurgecodeisnotautomaticallypurgingWRM$_SNAPSHOT_DETAILS,asexpected

Evenafterdroppingarangeofsnapid'susingdbms_workload_repository.drop_snapshot_range(),thetableisnotpurged.

TableWRM$_SNAPSHOT_DETAILSgrowsindefinitely.

TherearemanyorphanedentriesinthetableWRM$_SNAPSHOT_DETAILS.

ThenumberoforphanedrowsforthetableWRM$_SNAPSHOT_DETAILScanbefoundbyrunningthefollowingsql:

SQL>SELECTMIN(snap_id),
max(snap_id),
cast(min(begin_time)asdate)"MinBeginTime",
CAST(MAX(begin_time)ASDATE)"MaxBeginTime",
COUNT(*)
FROMsys.wrm$_snapshot_detailsa
WHERENOTEXISTS
(SELECT*
FROMsys.wrm$_snapshotb
WHEREb.snap_id=a.snap_id
ANDa.dbid=b.dbid
anda.instance_number=b.instance_number
)

MIN(SNAP_ID)MAX(SNAP_ID)MinBeginTimeMaxBeginTimeCOUNT(*)
--------------------------------------------------------------------------
1699329-nov-201121:00:0124-sep-201222:00:17577574


CAUSE
Thisissueiscausedbyanunpublishedbug:

[align=left]Document9797851.8Bug9797851-WRM$_SNAPHOST_DETAILSisneverpurged[/align]
Theverificationcriteriaforthebugare:

Droparangeofsnapid'susingdbms_workload_repository.drop_snapshot_range()

Checkthecorrespondingsnapid'sinWRM$_SNAPSHOT_DETAILS.

Ifsnapid'sfromtherangethatyouchosetodroparestillpresent,thenyouarehittingthisbug.

SOLUTION
Thefollowingsolutionsareavailable:

ThePatch9797851forunpublishedBug9797851isavailableforsomeplatformsandcanbedownloadedfromMyOracleSupport

Ifthepatchisnotavailableonyourplatformonasupportedversion,pleasecontactOracleSupport.

ThisissuewillbefixedfromreleaseOracle12.1

Asaworkaround,itispossibletomanuallypurgetherangeofsnapid'sfromthetableWRM$_SNAPSHOT_DETAILSusingappropriatedeletestatmentsundertheguidanceofOracleSupport.

Note:

在下面版本中，这些bug才fix掉了，请留意自己的版本信息。




                                            

                                        

                        
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