案例：AWR手工创建快照失败，SYSAUX表空间剩余不足处理
1. 查看SYSAUX表空间的段大小
查看SYSAUX表空间的段大小，按大小排序：
select segment_name, sum(bytes) / 1024 / 1024
from dba_segments
where tablespace_name = 'SYSAUX'
group by segment_name
order by 2;最大的结果列表：
SEGMENT_NAME SUM(BYTES)/1024/1024
------------------------------ --------------------
WRH$_SYSMETRIC_HISTORY_INDEX 80
WRH$_DLM_MISC_PK 80.0625
WRH$_DLM_MISC 96.0625
WRH$_EVENT_HISTOGRAM 688.0625
WRH$_EVENT_HISTOGRAM_PK 1008.0625
WRH$_ACTIVE_SESSION_HISTORY_PK 3016.0625
WRH$_ACTIVE_SESSION_HISTORY 22373.0625
4462 rows selected.发现最大的对象是WRH$_ACTIVE_SESSION_HISTORY，这里占了22G的大小，另外其对应的主键索引也占了3G。
2. AWR快照列表是空
查看AWR列表：
@?/rdbms/admin/awrrptAWR快照列表是空
Listing all Completed Snapshots
尝试手工创建快照也会失败，明确提示是SYSAUX表空间剩余不足，无法扩展。
exec DBMS_WORKLOAD_REPOSITORY.create_snapshot();3. 清理回收表空间
根据MOS文档 WRH$_ACTIVE_SESSION_HISTORY Does Not Get Purged Based Upon the Retention Policy (文档 ID 387914.1)
查询表空间使用率：
set lines 400 pages 999
select TABLESPACE_NAME,(TABLESPACE_SIZE-USED_SPACE)*8/1024/1024 free_space, USED_SPACE*8/1024/1024 USED_SPACE,TABLESPACE_SIZE*8/1024/1024 TABLESPACE_SIZE,USED_PERCENT from DBA_TABLESPACE_USAGE_METRICS order by 5 ;SYSAUX 3.60882568 28.3911591 31.9999847 88.7224144
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查询WRH$_ACTIVE_SESSION_HISTORY的分区信息：
SELECT owner,
segment_name,
partition_name,
segment_type,
bytes/1024/1024/1024 Size_GB
FROM dba_segments
WHERE segment_name='WRH$_ACTIVE_SESSION_HISTORY';结果如下：
OWNER SEGMENT_NAME PARTITION_NAME SEGMENT_TYPE SIZE_GB
------------------------------ ------------------------------ ------------------------------ ------------------ ----------
SYS WRH$_ACTIVE_SESSION_HISTORY WRH$_ACTIVE_1154052622_0 TABLE PARTITION 21.7900391
SYS WRH$_ACTIVE_SESSION_HISTORY WRH$_ACTIVE_SES_MXDB_MXSN TABLE PARTITION .000061035根据MOS的说明操作：
alter session set "_swrf_test_action" = 72;经过这一步之后，发现分割出一个分区，而且实际发现SYSAUX表空间释放出3G的空间，这里思考一下，分割分区并不会导致空间下降，推测有可能是分割的操作触发了自动删除的条件。
结果如下(多了一个分区)：
OWNER SEGMENT_NAME PARTITION_NAME SEGMENT_TYPE SIZE_GB
------------------------------ ------------------------------ ------------------------------ ------------------ ----------
SYS WRH$_ACTIVE_SESSION_HISTORY WRH$_ACTIVE_1154052622_0 TABLE PARTITION 21.7900391
SYS WRH$_ACTIVE_SESSION_HISTORY WRH$_ACTIVE_1154052622_5093 TABLE PARTITION .05859375
SYS WRH$_ACTIVE_SESSION_HISTORY WRH$_ACTIVE_SES_MXDB_MXSN TABLE PARTITION .000061035此时，根据MOS文档说明，执行：
set serveroutput on
declare
CURSOR cur_part IS
SELECT partition_name from dba_tab_partitions
WHERE table_name = 'WRH$_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;
/得到结果如下：
PARTITION NAME SNAP_ID DBID
--------------------------- ------- ----------
WRH$_ACTIVE_1154052622_5093 Min 5093 1154052622
WRH$_ACTIVE_1154052622_5093 Max 5210 1154052622
---
WRH$_ACTIVE_1154052622_0 Min 1 1154052622
WRH$_ACTIVE_1154052622_0 Max 5092 1154052622
---MOS上清空历史分区的方法：
DBMS_WORKLOAD_REPOSITORY.DROP_SNAPSHOT_RANGE(
low_snap_id IN NUMBER,
high_snap_id IN NUMBER
dbid IN NUMBER DEFAULT NULL);实际如果执行就是：
exec DBMS_WORKLOAD_REPOSITORY.DROP_SNAPSHOT_RANGE(1,5092);
--如果不是本地的dbid，那就第三个参数值填上对应dbid的参数即可,当然这里不需要加：
exec DBMS_WORKLOAD_REPOSITORY.DROP_SNAPSHOT_RANGE(1,5092,1154052622);但经过测试上一种MOS提到的方法比较慢，而且不立即释放空间。
所以如果想立即释放表空间，可以考虑评估直接truncate此表的对应分区（反复确认好后再操作）：
截断分区前查询表空间使用率：
set lines 400 pages 999
select TABLESPACE_NAME,(TABLESPACE_SIZE-USED_SPACE)*8/1024/1024 free_space, USED_SPACE*8/1024/1024 USED_SPACE,TABLESPACE_SIZE*8/1024/1024 TABLESPACE_SIZE,USED_PERCENT from DBA_TABLESPACE_USAGE_METRICS order by 5 ;
SYSAUX 3.60784912 28.3921356 31.9999847 88.7254661truncate历史分区WRH$_ACTIVE_1154052622_0
SQL> alter table WRH$_ACTIVE_SESSION_HISTORY truncate partition WRH$_ACTIVE_1154052622_0;
Table truncated.再次查询表空间使用率(已发现SYSAUX表空间使用率下降成功)：
SYSAUX 28.3323364 3.66764832 31.9999847 11.4614065再次查询WRH$_ACTIVE_SESSION_HISTORY的分区信息：
OWNER SEGMENT_NAME PARTITION_NAME SEGMENT_TYPE SIZE_GB
------------------------------ ------------------------------ ------------------------------ ------------------ ----------
SYS WRH$_ACTIVE_SESSION_HISTORY WRH$_ACTIVE_1154052622_5093 TABLE PARTITION .059570313
SYS WRH$_ACTIVE_SESSION_HISTORY WRH$_ACTIVE_SES_MXDB_MXSN TABLE PARTITION .000061035
SYS WRH$_ACTIVE_SESSION_HISTORY WRH$_ACTIVE_1154052622_0 TABLE PARTITION .000061035至此，完成WRH$_ACTIVE_SESSION_HISTORY的分区清理，SYSAUX表空间得到释放。