In this Document
Symptoms
Cause
Solution
References
Symptoms
sysaux表空間的WRH$_ACTIVE_SESSION_HISTORY表變得很大，把SYSAUX表空間撐得報警。
Cause
AWR 表沒有根據sys.wrm$_wr_control的設定清除數據，行數不斷累積，表段變得非常的大。
Solution
從dba_hist_wr_control視圖查看當前的快照保留時間
SQL> select a.snap_interval,a.retention,a.topnsql from dba_hist_wr_control a;
SNAP_INTERVAL RETENTION TOPNSQL
-------------------------------------------------- -------------------------------------------------- ------------------------------
+00000 01:00:00.0 +00007 00:00:00.0 100
從dba_hist_snapshot視圖查看當前快照id
SELECT * FROM dba_hist_snapshot t ORDER BY t.snap_id ASC;
如下程式會從WRH$_ACTIVE_SESSION_HISTORY 表中得到一個最小和最大的snap id
set serveroutput on
declare
CURSOR cur_part IS
SELECT partition_name from dba_tab_partitions
WHERE table_name = 'WRH$_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;
>EXECUTE DBMS_WORKLOAD_REPOSITORY.DROP_SNAPSHOT_RANGE(102, 105); --選擇清除一個快照範圍
實際去測試這句的時候，不知道是卡很久還是太慢，沒有成功。使用之前需再次測試。
>alter table WRH$_ACTIVE_SESSION_HISTORY shrink space; --把表縮小
另一種方式
alter session set "_swrf_test_action" = 72;
會將WRH$_ACTIVE_SESSION_HISTORY分區表劃分成更細的一個分區表（SYSAUX表空間下的其他分區表其實也會被分多一個分區）
然後我直接將那個小分區給幹掉了，這樣做會刪掉最小那個分區全部的snapshot
SQL> alter table WRH$_ACTIVE_SESSION_HISTORY drop partition WRH$_ACTIVE_1015375936_0 ;
Table altered.
重複運行上面的alter session set "_swrf_test_action" = 72;會重新建立一個分區。
我麼刪掉了快照歷史，去看ASH報告，就會得到沒有數據的提示。
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Reference
【1】WRH$_ACTIVE_SESSION_HISTORY Does Not Get Purged Based Upon the Retention Policy (Doc ID 387914.1)
【2】 http://blog.itpub.net/26764973/viewspace-1853612/