Oracle dba_tablespace_usage_metrics 视图 查看表空间 说明
一.DBA_TABLESPACE_USAGE_METRICS 视图的理论说明
群里一朋友说使用dba_tablespace_usage_metrics 视图查看表空间的结果不正确,如下:
dba_tablespace_usage_metrics视图在oracle 10g中引入,但未公开。 到了Oracle11g公开了这个视图。因为在Oracle 10g里可以使用这个视图,但是在官网文档里看不到说明,但是在11g的官方文档里可以查看到该视图的说明。
Oracle 11g中对这个视图的说明如下:
DBA_TABLESPACE_USAGE_METRICS describestablespace usage metrics for all types of tablespaces, including permanent,temporary, and undo tablespaces.
Column | Datatype | NULL | Description |
TABLESPACE_NAME | VARCHAR2(30) |
| Tablespace name |
USED_SPACE | NUMBER |
| Total space consumed by the tablespace(blocks) |
TABLESPACE_SIZE | NUMBER |
| Total size of the tablespace(blocks) |
USED_PERCENT | NUMBER |
| Percentage of used space, as a function of the maximum possible tablespace size(USED_SPACE / TABLESPACE_SIZE * 100) |
从官网的说明,这个视图很方便,通过DBA_TABLESPACE_USAGE_METRICS视图就可以查看所有类型表空间的使用情况,包括永久,临时和undo 表空间。
Oracle的文档也说的不够详细。上面表格中的括号部分Dave的补充。 DBA_TABLESPACE_USAGE_METRICS
视图中的USED_SPACE和TABLESPACE_SIZE的单位是block。默认情况下,oracle的每个block 是8k。
我们先查看DBA_TABLESPACE_USAGE_METRICS视图的创建代码:
SQL> select * from v$version;
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise EditionRelease 11.2.0.3.0 - 64bit Production
PL/SQL Release 11.2.0.3.0 - Production
CORE 11.2.0.3.0 Production
TNS for Linux: Version 11.2.0.3.0 -Production
NLSRTL Version 11.2.0.3.0 – Production
SQL> set pagesize 500
SQL> set long 999999
SQL> select text from dba_views where view_name='DBA_TABLESPACE_USAGE_METRICS';
TEXT
--------------------------------------------------------------------------------
SELECT t.name,
tstat.kttetsused,
tstat.kttetsmsize,
(tstat.kttetsused / tstat.kttetsmsize) * 100
FROM sys.ts$ t, x$kttets tstat
WHERE
t.online$ != 3 and
t.bitmapped <> 0 and
t.contents$ = 0 and
bitand(t.flags, 16) <> 16 and
t.ts# = tstat.kttetstsn
union
SELECT t.name, sum(f.allocated_space),sum(f.file_maxsize),
(sum(f.allocated_space)/sum(f.file_maxsize))*100
FROM sys.ts$ t, v$filespace_usage f
WHERE
t.online$ != 3 and
t.bitmapped <> 0 and
t.contents$ <> 0 and
f.flag = 6 and
t.ts# = f.tablespace_id
GROUP BY t.name, f.tablespace_id, t.ts#
union
SELECT t.name, sum(f.allocated_space),sum(f.file_maxsize),
(sum(f.allocated_space)/sum(f.file_maxsize))*100
FROM sys.ts$ t, gv$filespace_usage f, gv$parameter param
WHERE
t.online$ != 3 and
t.bitmapped <> 0 and
f.inst_id = param.inst_id and
param.name = 'undo_tablespace' and
t.name = param.value and
f.flag = 6 and
t.ts# = f.tablespace_id
GROUP BY t.name, f.tablespace_id, t.ts#
SQL>
通过上面的代码,我们可以看到,DBA_TABLESPACE_USAGE_METRICS说能查询所有类型的表空间,其本质也是进行了3个union。其关键数据还是出自:v$filespace_usage 视图。
官网对v$filespace_usage 视图的说明如下:
V$FILESPACE_USAGE summarizes spaceallocation information of each datafile and tempfile.
Column | Datatype | Description |
TABLESPACE_ID | NUMBER | ID of the tablespace to which the file belongs |
RFNO | NUMBER | Relative file number of the file |
ALLOCATED_SPACE | NUMBER | Total allocated space in the file |
FILE_SIZE | NUMBER | Current file size |
NUMBER | Maximum file size | |
CHANGESCN_BASE | NUMBER | SCN base of the last change to the file |
CHANGESCN_WRAP | NUMBER | SCN wrap of the last change to the file |
FLAG | NUMBER | Flags for file attributes |
根据以上的分析,我们可以得出一个结论:
1. DBA_TABLESPACE_USAGE_METRICS的USED_SPACE是已经分配的空间,对应V$FILESPACE_USAGE的ALLOCATED_SPACE的字段。
2. DBA_TABLESPACE_USAGE_METRICS的TABLESPACE_SIZE对应V$FILESPACE_USAGE的FILE_MAXSIZE字段。 这里对应的是最大值,如果我们的数据文件是自增长的,那么对于8k的block,那么这里的最大值就是32G。也就是最开始显示的4194302个blocks。
这个值与我们使用传统的DBA_DATA_FILES和DBA_FREE_SPACE查询的结果就会有很大的出入。
/* Formatted on 2013/3/21 20:39:40(QP5 v5.185.11230.41888) */
SELECTD.TABLESPACE_NAME,
SPACE"SUM_SPACE(M)",
BLOCKSSUM_BLOCKS,
SPACE-NVL(FREE_SPACE,0) "USED_SPACE(M)",
ROUND((1 - NVL(FREE_SPACE,0) /SPACE)* 100, 2) "USED_RATE(%)",
FREE_SPACE "FREE_SPACE(M)"
FROM( SELECTTABLESPACE_NAME,
ROUND (SUM(BYTES)/(1024 * 1024),2) SPACE,
SUM (BLOCKS)BLOCKS
FROM DBA_DATA_FILES
GROUPBYTABLESPACE_NAME) D,
( SELECTTABLESPACE_NAME,
ROUND (SUM(BYTES)/(1024 * 1024),2) FREE_SPACE
FROM DBA_FREE_SPACE
GROUPBYTABLESPACE_NAME) F
WHERED.TABLESPACE_NAME =F.TABLESPACE_NAME(+)
ORDER BY"USED_RATE(%)"DESC;
二.测试
我们这里创建2个表空间永久的表空间:
1) TS1: 自增长
2) TS2:不增长
然后分别使用使用上面说的2种方法查询表空间的使用情况。
2.1 创建表空间
SQL> create tablespace TS1 datafile'/u01/app/oracle/oradata/dave/ts01.dbf' size 100M autoextend on next 10Mmaxsize 1G;
Tablespace created.
SQL> create tablespace TS2 datafile'/u01/app/oracle/oradata/dave/ts02.dbf' size 100M autoextend off;
Tablespace created.
2.2 使用2种方法查看表空间情况
SQL> col tablespace_name for a15
SQL> select * from DBA_TABLESPACE_USAGE_METRICSwhere tablespace_name in ('TS1','TS2');
TABLESPACE_NAME USED_SPACE TABLESPACE_SIZEUSED_PERCENT
--------------- ---------- ---------------------------
TS1 128 131072 .09765625
TS2 128 12800 1
SQL> SELECT D.TABLESPACE_NAME,
2 SPACE"SUM_SPACE(M)",
3 BLOCKS SUM_BLOCKS,
4 SPACE - NVL(FREE_SPACE, 0) "USED_SPACE(M)",
5 ROUND ( (1 - NVL(FREE_SPACE, 0) / SPACE) * 100, 2) "USED_RATE(%)",
6 FREE_SPACE"FREE_SPACE(M)"
7 FROM ( SELECT TABLESPACE_NAME,
8 ROUND (SUM(BYTES) / (1024 * 1024), 2) SPACE,
9 SUM (BLOCKS) BLOCKS
10 FROM DBA_DATA_FILES
11 GROUP BY TABLESPACE_NAME) D,
12 ( SELECT TABLESPACE_NAME,
13 ROUND (SUM (BYTES) / (1024* 1024), 2) FREE_SPACE
14 FROM DBA_FREE_SPACE
15 GROUP BY TABLESPACE_NAME) F
16 WHERE D.TABLESPACE_NAME = F.TABLESPACE_NAME(+) AND D.TABLESPACE_NAME in('TS1','TS2');
TABLESPACE_NAME SUM_SPACE(M) SUM_BLOCKSUSED_SPACE(M) USED_RATE(%) FREE_SPACE(M)
--------------- ------------ ----------------------- ------------ -------------
TS2 100 12800 1 1 99
TS1 100 12800 1 1 99
2.3 分别在2个表空间创建一样的表
SQL> create table D1 tablespace TS1 asselect * from dba_objects;
Table created.
SQL> insert into D1 select * fromdba_objects;
75489 rows created.
SQL> insert into D1 select * fromdba_objects;
75489 rows created.
SQL> insert into D1 select * fromdba_objects;
75489 rows created.
SQL> insert into D1 select * fromdba_objects;
75489 rows created.
SQL> commit;
Commit complete.
SQL> create table D2 tablespace TS2 asselect * from dba_objects;
Table created.
SQL> insert into D2 select * fromdba_objects;
75490 rows created.
SQL> insert into D2 select * fromdba_objects;
75490 rows created.
SQL> insert into D2 select * fromdba_objects;
75490 rows created.
SQL> insert into D2 select * fromdba_objects;
75490 rows created.
SQL> commit;
Commit complete.
2.4 再次查看表空间变化
SQL> select * from DBA_TABLESPACE_USAGE_METRICS where tablespace_name in('TS1','TS2');
TABLESPACE_NAME USED_SPACE TABLESPACE_SIZEUSED_PERCENT
--------------- ---------- ---------------------------
TS1 5632 131072 4.296875
TS2 5632 12800 44
注意:
我们TS1是最大表空间是131072。 因为我们创建TS1表空间时指定的大小是1G。所以我们计算一下:131072*8K/1024= 1024M =1G。这样就正好和我们第一节的理论知识保持一致。
通过对比我们也可以确定,我们TS1表空间实际使用的空间和TS2表空间一致,都是5632个block。但是在计算使用率的时候,就出现了偏差。所以对于自动增长的表空间,DBA_TABLESPACE_USAGE_METRICS 视图就不那么适用了。
SQL> SELECT D.TABLESPACE_NAME,
2 SPACE"SUM_SPACE(M)",
3 BLOCKS SUM_BLOCKS,
4 SPACE - NVL(FREE_SPACE, 0) "USED_SPACE(M)",
5 ROUND ( (1 - NVL(FREE_SPACE, 0) / SPACE) * 100, 2) "USED_RATE(%)",
6 FREE_SPACE"FREE_SPACE(M)"
7 FROM ( SELECT TABLESPACE_NAME,
8 ROUND (SUM(BYTES) / (1024 * 1024), 2) SPACE,
9 SUM (BLOCKS) BLOCKS
10 FROM DBA_DATA_FILES
11 GROUP BY TABLESPACE_NAME) D,
12 ( SELECT TABLESPACE_NAME,
13 ROUND (SUM (BYTES) / (1024* 1024), 2) FREE_SPACE
14 FROM DBA_FREE_SPACE
15 GROUP BY TABLESPACE_NAME) F
16 WHERE D.TABLESPACE_NAME = F.TABLESPACE_NAME(+) AND D.TABLESPACE_NAME in('TS1','TS2');
TABLESPACE_NAME SUM_SPACE(M) SUM_BLOCKSUSED_SPACE(M) USED_RATE(%) FREE_SPACE(M)
--------------- ------------ ----------------------- ------------ -------------
TS2 100 12800 44 44 56
TS1 100 12800 44 44 56
但我们通过DBA_DATA_FILES和DBA_FREE_SPACE查询结果就是一致的。
三.小结
通过上面的对比,dba_tablespace_usage_metrics视图对于非自动增长的表空间,和我们使用传统的DBA_DATA_FILES和DBA_FREE_SPACE查询的结果是一致的。
但是对于自动增长的表空间,dba_tablespace_usage_metrics的表空间就不准确了。还是要使用原始的方法来查询。
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