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：
- 当前schema5张表合计使用空间 42931.375 MB = 41.92517 GB
- users表空间的4个数据文件合计105767.5 MB = 103.28857GB
- 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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