undo表空间容量

查看表空间使用情况

SELECT a.tablespace_name,

ROUND (a.total_size) "total_size(MB)",

ROUND (a.total_size) - ROUND (b.free_size, 3) "used_size(MB)",

ROUND (b.free_size, 3) "free_size(MB)",

ROUND (b.free_size / total_size * 100, 2) || '%' free_rate

FROM ( SELECT tablespace_name, SUM (bytes) / 1024 / 1024 total_size

FROM dba_data_files

GROUP BY tablespace_name) a,

( SELECT tablespace_name, SUM (bytes) / 1024 / 1024 free_size

FROM dba_free_space

GROUP BY tablespace_name) b

WHERE a.tablespace_name = b.tablespace_name(+);

TABLESPACE_NAME total_size(MB) used_size(MB) free_size(MB) FREE_RATE

------------------------------ -------------- ------------- ------------- -----------------------------------------

SYSAUX 900 835.687 64.313 7.15%

UNDOTBS1 24576 53.875 24522.125 99.78%

USERS 5 1.312 3.688 73.75%

SYSTEM 4170 4160.687 9.313 .22%

USER_DATA 150 105.062 44.938 29.96%

计算所需undo表空间的大小:

1.计算业务高峰期每秒产生undo数据块的个数

SQL> select max(undoblks / ((end_time - begin_time)*24*3600)) from v$undostat;

MAX(UNDOBLKS/((END_TIME-BEGIN_

------------------------------

11.305

2.得到undo数据块在undo表空间中可以保留的最长时间

SQL> show parameter undo_retention;

NAME TYPE VALUE

------------------------------------ ----------- ------------------------------

undo_retention integer 86400

3.得到数据块大小

SQL> show parameter db_blo

NAME TYPE VALUE

------------------------------------ ----------- ------------------------------

db_block_buffers integer 0

db_block_checking string FALSE

db_block_checksum string TYPICAL

db_block_size integer 8192

4.将以上三者的数据相乘就是所需undo表空间的大小数

SQL> select (11.305*86400*8192)/1024/1024/1024 undoTablespace_GB from dual;

UNDOTABLESPACE_GB

-----------------

7.4520263671875

发现undo表空间不够的时候，赶紧增加undo表空间的大小，执行语句如下：

alter tablespace undotbs1 add datafile '/u01/database/instance_name/undotbs02.dbf' size 100M autoextend on next 128M maxsize 24G;

alter tablespace undotbs1 add datafile '/u01/database/instance_name/undotbs03.dbf' size 100M autoextend on next 128M maxsize 24G;

alter tablespace undotbs1 add datafile '/u01/database/instance_name/undotbs04.dbf' size 100M autoextend on next 128M maxsize 24G;

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