oracle中段有什么用？

Time_Will_Tell 2010-12-17 11:38:31

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最好举实际例，对段的操作之类的。
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Oraclefans_ 2010-12-17

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段就可以认为是数据库的对象。你在进行表，索引等进行操作的时候就会建立一个相应的段。
他展示数据库的对象在数据文件里的存储信息和存储的分配。

DBA_SEGMENTS describes the storage allocated for all segments in the database.



SQL> conn sys/myorcl as sysdba;

Connected to Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 

Connected as SYS

-----刚开始没有我想创建的对象tiny.tests

SQL> select * from dba_segments r where r.owner = 'TINY' and r.segment_name = 'TESTS';



OWNER                          SEGMENT_NAME                                                                     PARTITION_NAME                 SEGMENT_TYPE       TABLESPACE_NAME                HEADER_FILE HEADER_BLOCK      BYTES     BLOCKS    EXTENTS INITIAL_EXTENT NEXT_EXTENT MIN_EXTENTS MAX_EXTENTS PCT_INCREASE  FREELISTS FREELIST_GROUPS RELATIVE_FNO BUFFER_POOL

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



SQL> create table tiny.tests(id number);



Table created



SQL> select * from dba_segments r where r.owner = 'TINY' and r.segment_name = 'TESTS';



OWNER                          SEGMENT_NAME                                                                     PARTITION_NAME                 SEGMENT_TYPE       TABLESPACE_NAME                HEADER_FILE HEADER_BLOCK      BYTES     BLOCKS    EXTENTS INITIAL_EXTENT NEXT_EXTENT MIN_EXTENTS MAX_EXTENTS PCT_INCREASE  FREELISTS FREELIST_GROUPS RELATIVE_FNO BUFFER_POOL

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

TINY                           TESTS                                                                                                           TABLE              USERS                                    4          793      65536          8          1          65536                       1  2147483645                       1               1            4 DEFAULT



SQL> drop table tiny.tests;



Table dropped



SQL> select * from dba_segments r where r.owner = 'TINY' and r.segment_name = 'TESTS';



OWNER                          SEGMENT_NAME                                                                     PARTITION_NAME                 SEGMENT_TYPE       TABLESPACE_NAME                HEADER_FILE HEADER_BLOCK      BYTES     BLOCKS    EXTENTS INITIAL_EXTENT NEXT_EXTENT MIN_EXTENTS MAX_EXTENTS PCT_INCREASE  FREELISTS FREELIST_GROUPS RELATIVE_FNO BUFFER_POOL

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



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