我们知道,在Oracle 10g中,drop table如果没有加 purge选项.实际数据并没有删除,因而没有释放表空间.
那么当被删除的对象占用了所有空间时，会发生什么? 相信看完以下测试,一切皆会明白
| YXYUP@dbatest>selecttablespace_name,sum(bytes)/1024/1024 from dba_data_files where tablespace_name='TBS' group by tablespace_name; TABLESPACE_NAME SUM(BYTES)/1024/1024 -------------------- -------------------- TBS 17 Elapsed: 00:00:00.02 YXYUP@dbatest>selectsegment_name,bytes/1024/1024,tablespace_name from user_segments; SEGMENT_NAME BYTES/1024/1024 TABLESPACE_NAME ------------------------------ --------------- -------------------- TEST_BAK 6 TBS TEST01 6 TBS Elapsed: 00:00:00.07 YXYUP@dbatest>createtable test02 tablespace tbs as select * from dba_objects; create table test02 tablespace tbs as select * from dba_objects * ERROR at line 1: ORA-01652: unable to extend temp segment by 128 in tablespace TBS Elapsed: 00:00:00.73 YXYUP@dbatest>droptable test01; Table dropped. Elapsed: 00:00:00.04 YXYUP@dbatest>showrecyclebin; ORIGINAL NAME RECYCLEBIN NAME OBJECT TYPE DROP TIME ---------------- ------------------------------ ------------ ------------------- TEST01 BIN$VPH4ibnKVd/gQAB/AQA0Nw==$0 TABLE 2008-08-21:14:56:55 YXYUP@dbatest> YXYUP@dbatest>select* from tab; TNAME TABTYPE CLUSTERID ------------------------------ ------- ---------- BIN$VPH4ibnKVd/gQAB/AQA0Nw==$0 TABLE TEST_BAK TABLE Elapsed: 00:00:00.01 YXYUP@dbatest>createtable test02 tablespace tbs as select * from dba_objects; Table created. Elapsed: 00:00:00.84 YXYUP@dbatest>showrecyclebin; YXYUP@dbatest>select* from tab; TNAME TABTYPE CLUSTERID ------------------------------ ------- ---------- TEST_BAK TABLE TEST02 TABLE Elapsed: 00:00:00.01 |
上面测试可以看出,当表空间空闲空间不足时,Oracle就会将recyclebin中的表给彻底删除,然后腾出空间来放要创建的新对象.
那么,如果recyclebin中有多个被drop的对象时,Oracle会怎么清理呢,是全部清除,还是怎样? 通过下面的测试我们行到答案.
| YXYUP@dbatest>showrecyclebin; YXYUP@dbatest>select* from tab; TNAME TABTYPE CLUSTERID ------------------------------ ------- ---------- TEST_BAK TABLE TEST02 TABLE Elapsed: 00:00:00.01 YXYUP@dbatest>droptable test02; Table dropped. Elapsed: 00:00:00.04 YXYUP@dbatest>droptable test_bak; Table dropped. Elapsed: 00:00:00.02 YXYUP@dbatest>select* from tab; TNAME TABTYPE CLUSTERID ------------------------------ ------- ---------- BIN$VPH4ibnLVd/gQAB/AQA0Nw==$0 TABLE BIN$VPH4ibnMVd/gQAB/AQA0Nw==$0 TABLE Elapsed: 00:00:00.01 YXYUP@dbatest>showrecyclebin; ORIGINAL NAME RECYCLEBIN NAME OBJECT TYPE DROP TIME ---------------- ------------------------------ ------------ ------------------- TEST02 BIN$VPH4ibnLVd/gQAB/AQA0Nw==$0 TABLE 2008-08-21:15:14:43 TEST_BAK BIN$VPH4ibnMVd/gQAB/AQA0Nw==$0 TABLE 2008-08-21:15:14:51 YXYUP@dbatest>createtable test01 tablespace tbs as select * from dba_objects; Table created. Elapsed: 00:00:00.79 YXYUP@dbatest>select* from tab; TNAME TABTYPE CLUSTERID ------------------------------ ------- ---------- BIN$VPH4ibnMVd/gQAB/AQA0Nw==$0 TABLE TEST01 TABLE Elapsed: 00:00:00.01 YXYUP@dbatest>flashbacktable TEST02 to before drop ; flashback table TEST02 to before drop * ERROR at line 1: ORA-38305: object not in RECYCLE BIN Elapsed: 00:00:00.00 YXYUP@dbatest>flashbacktable TEST_BAK to before drop ; Flashback complete. Elapsed: 00:00:00.02 YXYUP@dbatest>select* from tab; TNAME TABTYPE CLUSTERID ------------------------------ ------- ---------- TEST_BAK TABLE TEST01 TABLE Elapsed: 00:00:00.01 |
通过上面测试可以看出.
当recyclebin中有多个被删除的同时,并在表空间不足以放下要创建的新对象时,Oracle会FIFO的方式从回收站中自动彻底删除.
