oracle11g UNDO使用率高，且unexpire过高

oracle11g UNDO使用率高，且unexpire过高

1、查看使用率：

set lines 2000
col USED_PER for a60
SELECT A.TABLESPACE_NAME AS TABLESPACE_NAME,
       ROUND(TOTAL/1024/1024/1024,3) AS TOTAL_GB,
       ROUND(FREE/1024/1024/1024,2) AS FREE_GB,
       ROUND(( TOTAL - FREE )/1024/1024/1024,2) AS USED_GB,
       TO_CHAR(ROUND(( TOTAL - FREE ) / TOTAL * 100, 2),'90.99')||'%' AS USED_PER
FROM   (SELECT TABLESPACE_NAME,
               SUM(BYTES) FREE
        FROM   DBA_FREE_SPACE
        GROUP  BY TABLESPACE_NAME) A,
       (SELECT TABLESPACE_NAME,
               SUM(BYTES) TOTAL
        FROM   DBA_DATA_FILES
        GROUP  BY TABLESPACE_NAME) B
WHERE  A.TABLESPACE_NAME = B.TABLESPACE_NAME
order by USED_PER desc;

2、查看各状态undo使用情况统计

select tablespace_name,status,sum(bytes)/1024/1024 MB from dba_undo_extents
where tablespace_name like 'UNDOTBS%'
group by tablespace_name,status
order by 1;

3、查看数据文件是否自动扩展

 select TABLESPACE_NAME,FILE_NAME,BYTES/1024/1024/1024 Gb,AUTOEXTENSIBLE from  dba_data_files where TABLESPACE_NAME  like '%UNDO%'; 

经过查看，目前undo datafile 均为非自动扩展.

4、拼接sql，设置undo数据文件为自动扩展

select 'ALTER DATABASE DATAFILE '||d.file_id||'  AUTOEXTEND ON MAXSIZE '||((bytes/1024/1024) +1) ||'M;' from dba_data_files d where d.tablespace_name like '%UNDO%';

执行拼接的sql，经过几分钟，查询使用率可看到undo使用率在减小，unexpire过高的情况明显改善。

5、后续

过了两天继续跟进查看，发现undo使用率明显减少，从之前的占用90GB降低到占用7GB，效果显著！