简而言之，flashback drop就是将已经被drop的表从recycebin中恢复回来，表被drop后，实际上只是改了个名，并没有释放空间。

1. 启用和禁用recyclebin：

ALTER SESSION SET recyclebin = OFF;

ALTER SYSTEM SET recyclebin = OFF;

ALTER SESSION SET recyclebin = ON;

ALTER SYSTEM SET recyclebin = ON;

2.使用recyclebin进行flashback drop

SQL> create table test tablespace users as select * from dba_objects;

Table created.

SQL> select object_name,original_name,operation,type,ts_name,createtime,droptime from recyclebin;

no rows selected

SQL> drop table test;

Table dropped.

SQL> select object_name,original_name,operation,type,ts_name,createtime,droptime from recyclebin;

OBJECT_NAME ORIGINAL_N OPERATION TYPE TS_NAME CREATETIME DROPTIME

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

BIN$xRCsD3sxEqbgQAB/AQAqpw==$0 TEST DROP TABLE USERS 2012-07-18:09:42:38 2012-07-18:09:42:48

SQL> FLASHBACK TABLE test TO BEFORE DROP RENAME TO TEST_BAK;

Flashback complete.

SQL> select count(*) from test_bak;

COUNT(*)

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44940

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flashback技术之---flashback drop