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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$_SNAPSHOT_DETAILS表中数据的情况，测试服务器版本为10.2.0.5.0，AWR的快照是1小时采集一次数据，快照保留14天，也就是二周。具体情况如下所示：
SQL> select * from v$version;
BANNER
----------------------------------------------------------------Oracle Database 10g Release 10.2.0.5.0 - 64bit ProductionPL/SQL Release 10.2.0.5.0 - ProductionCORE 10.2.0.5.0 Production
TNS for Linux: Version 10.2.0.5.0 - ProductionNLSRTL Version 10.2.0.5.0 - Production
SQL> COL SNAP_INTERVAL FOR A20;
SQL> COL TETENTION FOR A26;
SQL> SELECT * FROM dba_hist_wr_control;
DBID SNAP_INTERVAL RETENTION TOPNSQL
---------- -------------------- --------------------------- ----------3990839260 +00000 01:00:00.0 +00014 00:00:00.0 DEFAULTSQL> SELECT MIN(SNAP_ID), MAX(SNAP_ID) FROM dba_hist_snapshot;
MIN(SNAP_ID) MAX(SNAP_ID)
------------ ------------ 7417 59195SQL> 
SQL> SELECT MIN(SNAP_ID), MAX(SNAP_ID) FROM dba_hist_snapshot;
MIN(SNAP_ID) MAX(SNAP_ID)
------------ ------------ 7417 59196SQL> select dbid, status, count(*)
2 from wrm$_snapshot3 group by dbid, status;
DBID STATUS COUNT(*)---------- ---------- ----------3990839260 0 1250SQL> select min(snap_id), max(snap_id), dbid from wrm$_snapshot
2 group by dbid;
MIN(SNAP_ID) MAX(SNAP_ID) DBID
------------ ------------ ---------- 7417 59196 3990839260SQL> exec dbms_workload_repository.drop_snapshot_range(7417,59196,3990839260);
PL/SQL procedure successfully completed.
SQL> select min(snap_id), max(snap_id), dbid from wrm$_snapshot
2 group by dbid;
MIN(SNAP_ID) MAX(SNAP_ID) DBID
------------ ------------ ---------- 7417 59197 3990839260SQL> select min(snap_id), max(snap_id), dbid from wrm$_snapshot
2 group by dbid;
MIN(SNAP_ID) MAX(SNAP_ID) DBID
------------ ------------ ---------- 7417 59197 3990839260SQL> SELECT MIN(SNAP_ID), MAX(SNAP_ID) FROM dba_hist_snapshot;
MIN(SNAP_ID) MAX(SNAP_ID)
------------ ------------
7417 59197
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$_SNAPSHOT_DETAILS，使用下面SQL就能查看具体定义
SELECT OWNER, VIEW_NAME, TEXT FROM DBA_VIEWS WHERE VIEW_NAME=‘DBA_HIST_SNAPSHOT‘;
"select snap_id, dbid, instance_number, startup_time,begin_interval_time, end_interval_time,
flush_elapsed, snap_level, error_count
from WRM$_SNAPSHOTwhere status = 0"
其实这个是一个Bug引起的，官方文档WRM$_SNAPSHOT_DETAILS Table is Not Purged (文档 ID 1489801.1) 和文档 Document 9797851.8 Bug 9797851 - WRM$_SNAPHOST_DETAILS is never purged 都有描述这个Bug
The following symptoms are observed:
The number of orphaned rows for the table WRM$_SNAPSHOT_DETAILS can be found by running the following sql:
SQL> SELECT MIN(snap_id),
max(snap_id) ,
cast(min(begin_time) as date) "Min Begin Time",
CAST(MAX(begin_time) AS DATE) "Max Begin Time",
COUNT(*)
FROM sys.wrm$_snapshot_details a
WHERE NOT EXISTS
(SELECT *
FROM sys.wrm$_snapshot b
WHERE b.snap_id = a.snap_id
AND a.dbid = b.dbid
and a.instance_number = b.instance_number
)
MIN(SNAP_ID) MAX(SNAP_ID) Min Begin Time Max Begin Time COUNT(*)
------------ ------------ -------------------- -------------------- ----------
1 6993 29-nov-2011 21:00:01 24-sep-2012 22:00:17 577574
This issue is caused by an unpublished bug:
The verification criteria for the bug are:
The following solutions are available:
As a workaround, it is possible to manually purge the range of snap id‘s from the table WRM$_SNAPSHOT_DETAILS using appropriate delete statments under the guidance of Oracle Support.
Note:
在下面版本中，这些bug才fix掉了，请留意自己的版本信息。
DROP_SNAPSHOT_RANGE过程不能清理表RM$_SNAPSHOT_DETAILS
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原文地址：http://www.cnblogs.com/kerrycode/p/5631564.html
