一个查看Oracle表和表空间存储分配的示例

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从以下输出可知,在当前schema中,空间占用约43GB,使用的是users表空间。

SQL> show parameter db_block_size

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_block_size                        integer     8192

col segment_name for a20
col tablespace_name for a16
select segment_name, tablespace_name, bytes/1024/1024, blocks*8/1024 from user_segments;

SEGMENT_NAME         BYTES/1024/1024 BLOCKS*8/1024
-------------------- --------------- -------------
CUSTOMER                          30            30
DATE_DIM                        .375          .375
LINEORDER                      42795         42795
PART                             104           104
SUPPLIER                           2             2

SQL> select  sum(bytes)/1024/1024, sum(blocks)*8/1024 from user_segments;

SUM(BYTES)/1024/1024 SUM(BLOCKS)*8/1024
-------------------- ------------------
           42931.375          42931.375

再来看下extent的情况,可知在当前schema有5个table segment:

set pages 9999
select segment_type, count(1) from dba_segments group by segment_type order by segment_type;

SEGMENT_TYPE         COUNT(1)
------------------ ----------
CLUSTER                    10
INDEX                     774
INDEX PARTITION            29
LOB PARTITION              28
LOBINDEX                  400
LOBSEGMENT                400
NESTED TABLE               11
ROLLBACK                    1
SYSTEM STATISTICS           1
TABLE                     590
TABLE PARTITION            42
TYPE2 UNDO                 10

12 rows selected.

SQL> select segment_type, count(1) from user_segments group by segment_type order by segment_type;

SEGMENT_TYPE         COUNT(1)
------------------ ----------
TABLE                       5

看一下分布详情,注意这里用user_extents是不行的:

select tablespace_name, file_id, extent_id, block_id, blocks, bytes from dba_extents where owner='SSB' and segment_name='LINEORDER';

TABLESPACE_NAME     FILE_ID  EXTENT_ID   BLOCK_ID     BLOCKS      BYTES
---------------- ---------- ---------- ---------- ---------- ----------
USERS                    12          0    3923248          8      65536
USERS                    12          1    3923256          8      65536
USERS                    12          2    3923264          8      65536
USERS                    12          3    3923272          8      65536
...
USERS                    12        850     721408       8192   67108864
USERS                    18        851    1368576       8192   67108864
USERS                    17        852    1368576       8192   67108864
USERS                    16        853    1368576       8192   67108864

854 rows selected.

输出太多,我们简化一下,可知lineorder表均匀分布在users表空间的4个数据文件上:

SQL> select sum(blocks)*8/1024, sum(bytes)/1024/1024 from dba_extents where owner='SSB' and segment_name='LINEORDER';

SUM(BLOCKS)*8/1024 SUM(BYTES)/1024/1024
------------------ --------------------
             42795                42795

SQL> select tablespace_name, file_id, sum(blocks)*8/1024, sum(bytes)/1024/1024 from dba_extents where owner='SSB' and segment_name='LINEORDER' group by tablespace_name, file_id;

TABLESPACE_NAME     FILE_ID SUM(BLOCKS)*8/1024 SUM(BYTES)/1024/1024
---------------- ---------- ------------------ --------------------
USERS                    12          10621.625            10621.625
USERS                    16              10746                10746
USERS                    18          10737.375            10737.375
USERS                    17              10690                10690

再来看一下表空间情况:

set lines 140
col file_name for a100
select tablespace_name,file_name from dba_data_files where file_id in
(select distinct(file_id) from dba_extents where owner='SSB' and segment_name='LINEORDER');

TABLESPACE_NAME  FILE_NAME
---------------- ----------------------------------------------------------------------------------------------------
USERS            +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/users.274.1115978849
USERS            +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/users.286.1116135705
USERS            +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/users.287.1116135705
USERS            +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/users.285.1116135699

users表空间每个数据文件多大?数据文件的大小并不表示数据的大小。因为users表空间的4个数据文件合计105GB,但当前schema的5张表使用空间为43GB。

col tsname for a16
col filename for a100
select t.name tsname, d.name filename, d.bytes/1024/1024 from v$tablespace t join v$datafile d using(ts#) union all select t.name,d.name, d.bytes from v$tablespace t join v$tempfile d using(ts#);

TSNAME           FILENAME                                                                                             D.BYTES/1024/1024
---------------- ---------------------------------------------------------------------------------------------------- -----------------
SYSTEM           +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/system.273.1115978715                                400
SYSAUX           +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/sysaux.270.1115978723                                520
UNDOTBS1         +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/undotbs1.275.1115978855                             1485
USERS            +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/users.274.1115978849                             32767.5
USERS            +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/users.285.1116135699                               24700
USERS            +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/users.286.1116135705                               23600
USERS            +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/users.287.1116135705                               24700
TEMP             +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/TEMPFILE/temp.272.1115978713                           4293918720

8 rows selected.

SQL> select t.name tsname, d.name filename, d.bytes/1024/1024 from v$tablespace t join v$datafile d using(ts#);

TSNAME           FILENAME                                                                                             D.BYTES/1024/1024
---------------- ---------------------------------------------------------------------------------------------------- -----------------
SYSTEM           +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/system.273.1115978715                                400
SYSAUX           +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/sysaux.270.1115978723                                520
UNDOTBS1         +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/undotbs1.275.1115978855                             1485
USERS            +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/users.274.1115978849                             32767.5
USERS            +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/users.285.1116135699                               24700
USERS            +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/users.286.1116135705                               23600
USERS            +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/users.287.1116135705                               24700

7 rows selected.

SQL> select t.name tsname, d.name filename, d.bytes/1024/1024 from v$tablespace t join v$datafile d using(ts#) where t.name = 'USERS';

TSNAME           FILENAME                                                                                             D.BYTES/1024/1024
---------------- ---------------------------------------------------------------------------------------------------- -----------------
USERS            +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/users.274.1115978849                             32767.5
USERS            +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/users.285.1116135699                               24700
USERS            +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/users.286.1116135705                               23600
USERS            +DATA/DB0921_NRT1MZ/E92E139443C62209E0539B00000AFD03/DATAFILE/users.287.1116135705                               24700

SQL> select t.name tsname, sum(d.bytes)/1024/1024 from v$tablespace t join v$datafile d using(ts#) where t.name = 'USERS' group by t.name;

TSNAME           SUM(D.BYTES)/1024/1024
---------------- ----------------------
USERS                          105767.5

从以下输出也可以印证,MAXBYTES表示数据文件最大为32GB,BYTES表示当前数据文件的大小,也就是高水位线,但并不表示数据量。

SQL> select file_id, tablespace_name, bytes/1024/1024, maxbytes/1024/1024 from dba_data_files where tablespace_name = 'USERS';

   FILE_ID TABLESPACE_NAME                BYTES/1024/1024 MAXBYTES/1024/1024
---------- ------------------------------ --------------- ------------------
        12 USERS                                  32767.5         32767.9844
        16 USERS                                    24700         32767.9844
        17 USERS                                    23600         32767.9844
        18 USERS                                    24700         32767.9844

从以下输出可知,users表空间为smallfile表空间。

SQL> select tablespace_name, bigfile, max_extents, max_size, segment_space_management from dba_tablespaces where tablespace_name = 'USERS';

TABLESPACE_NAME  BIG MAX_EXTENTS   MAX_SIZE SEGMEN
---------------- --- ----------- ---------- ------
USERS            NO   2147483645 2147483645 AUTO

SQL> select 2147483645*8/1024/1024 from dual;

2147483645*8/1024/1024
----------------------
                 16384

以上的MAX_SIZE指的是“Default maximum size of segments (in Oracle blocks)”。也就是16GB。

按照这里的描述:

A smallfile tablespace is a traditional Oracle tablespace, which can contain 1022 data files or temp files, each of which can contain up to approximately 4 million (2^22) blocks.

即每个表空间最多1022个数据文件,每个数据文件32GB。即smallfile表空间最大约32GB。bigfile表空间在block大小为8K时最大是32TB,但表空间只能有1个数据文件,因此管理会简便些。

如何看表空间的剩余空间?可以用DBA_FREE_SPACE

select tablespace_name,
       sum(bytes)/1024/1024/1024 tot_free, sum(blocks),
       count(*) chunks
from dba_free_space
group by tablespace_name  ;

TABLESPACE_NAME    TOT_FREE SUM(BLOCKS)     CHUNKS
---------------- ---------- ----------- ----------
SYSTEM           .002502441         328          2
SYSAUX           .032958984        4320          2
UNDOTBS1         .630065918       82584        635
USERS            61.3594971     8042512         30

select tablespace_name, file_id,
       bytes/1024/1024 free_mb, blocks
from dba_free_space where tablespace_name = 'USERS';

TABLESPACE_NAME     FILE_ID    FREE_MB     BLOCKS
---------------- ---------- ---------- ----------
USERS                    12          3        384
USERS                    12          3        384
USERS                    12       2237     286336
USERS                    12       3968     507904
USERS                    12       3968     507904
USERS                    12       3968     507904
USERS                    12       3968     507904
USERS                    12       3968     507904
USERS                    12          1        128
USERS                    12          3        384
USERS                    12         .5         64
USERS                    16          3        384
USERS                    16       1149     147072
USERS                    16       3968     507904
USERS                    16       3968     507904
USERS                    16       3968     507904
USERS                    16        891     114048
USERS                    17          3        384
USERS                    17          3        384
USERS                    17       1149     147072
USERS                    17       3968     507904
USERS                    17       3968     507904
USERS                    17       3759     481152
USERS                    18       .625         80
USERS                    18          3        384
USERS                    18       1149     147072
USERS                    18       3968     507904
USERS                    18       3968     507904
USERS                    18       3968     507904
USERS                    18        891     114048

30 rows selected.

select file_id,
       sum(bytes)/1024/1024 free_mb, sum(blocks)
from dba_free_space where tablespace_name = 'USERS' group by file_id;
   FILE_ID    FREE_MB SUM(BLOCKS)
---------- ---------- -----------
        12    22087.5     2827200
        17      12850     1644800
        18  13947.625     1785296
        16      13947     1785216

现在整个数据就可以说得通了:

  1. 当前schema5张表合计使用空间 42931.375 MB = 41.92517 GB
  2. users表空间的4个数据文件合计105767.5 MB = 103.28857GB
  3. users表空间剩余空间 61.3594971GB

前2项之差为61.363404GB。

参考

  • https://connor-mcdonald.com/2020/08/27/finding-free-space-on-your-database-taking-a-long-time/
  • OCA/OCP Oracle 数据库12c考试指南读书笔记:第15章: Oracle Storage

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