Oracle RECYCLEBIN

The recyclebin is a public synonym and it is based on the view user_recyclebin which in turn is based on sys.recyclebin$ table.

SQl> Select object_type,object_name from dba_objects where object_name='RECYCLEBIN';

OBJECT_TYPE     OBJECT_NAME
-----------------------------------------------
SYNONYM         RECYCLEBIN


SQL> desc recyclebin
 Name                                      Null?    Type
 ----------------------------------------- -------- ------------
 OBJECT_NAME                               NOT NULL VARCHAR2(30)
 ORIGINAL_NAME                                      VARCHAR2(32)
 OPERATION                                          VARCHAR2(9)
 TYPE                                               VARCHAR2(25)
 TS_NAME                                            VARCHAR2(30)
 CREATETIME                                         VARCHAR2(19)
 DROPTIME                                           VARCHAR2(19)
 DROPSCN                                            NUMBER
 PARTITION_NAME                                     VARCHAR2(32)
 CAN_UNDROP                                         VARCHAR2(3)
 CAN_PURGE                                          VARCHAR2(3)
 RELATED                                   NOT NULL NUMBER
 BASE_OBJECT                               NOT NULL NUMBER
 PURGE_OBJECT                              NOT NULL NUMBER
 SPACE                                              NUMBER


Related recyclebin objects:

SQL> SELECT SUBSTR(object_name,1,50),object_type,owner
FROM dba_objects
WHERE object_name LIKE '%RECYCLEBIN%';
/
SUBSTR(OBJECT_NAME,1,50)                           OBJECT_TYPE         OWNER
---------------------------      ------------------- ------------ ----------
RECYCLEBIN$                                        TABLE               SYS
RECYCLEBIN$_OBJ                                    INDEX               SYS
RECYCLEBIN$_TS                                     INDEX               SYS
RECYCLEBIN$_OWNER                                  INDEX               SYS
USER_RECYCLEBIN                                    VIEW                SYS
USER_RECYCLEBIN                                    SYNONYM             PUBLIC
RECYCLEBIN                                         SYNONYM             PUBLIC
DBA_RECYCLEBIN                                     VIEW                SYS
DBA_RECYCLEBIN                                     SYNONYM             PUBLIC

9 rows selected.


THE RECYCLE BIN

The Recycle Bin is a virtual container where all dropped objects reside. Underneath the covers, the objects are occupying the same space as when they were created. If table EMP was created in the USERS tablespace, the dropped table EMP remains in the USERS tablespace. Dropped tables and any associated objects such as indexes, constraints, nested tables, and other dependant objects are not moved, they are simply renamed with a prefix of BIN$$. You can continue to access the data in a
dropped table or even use Flashback Query against it. Each user has the same rights and privileges on Recycle Bin objects before it was dropped. You can view your dropped tables by querying the new RECYCLEBIN view. Objects in the Recycle Bin will remain in the database until the owner of the dropped objects decides to permanently remove them using the new PURGE command. The Recycle Bin objects are counted against a user's quota. But Flashback Drop is a non-intrusive feature. Objects in the Recycle Bin will be automatically purged by the space reclamation process if

o A user creates a new table or adds data that causes their quota to be exceeded.
o The tablespace needs to extend its file size to accommodate create/insert operations.

There are no issues with dropping the table, behaviour wise. It is the same as in 8i / 9i. The space is not released immediately and is accounted for within the same tablespace / schema after the drop.

When we drop a tablespace or a user there is NO recycling of the objects.

o Recyclebin does not work for SYS owned objects

EXAMPLE

SQL> SELECT * FROM v$version;
BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.1.0.2.0 - 64bi
PL/SQL Release 10.1.0.2.0 - Production
CORE    10.1.0.2.0      Production
TNS for Solaris: Version 10.1.0.2.0 - Production
NLSRTL Version 10.1.0.2.0 - Production

SQL> sho user
USER is "BH"

SQL> SELECT object_name,original_name,operation,type,dropscn,droptime
  2  FROM user_recyclebin
  3  /
no rows selected

SQL> CREATE TABLE t1(a NUMBER);
Table created.

SQL> DROP TABLE t1;
Table dropped.

SQL> SELECT object_name,original_name,operation,type,dropscn,droptime
  2  FROM user_recyclebin
  3  /
OBJECT_NAME                    ORIGINAL_NAME                    OPERATION TYPE                         DROPSCN DROPTIME
------------------------------ -------------------------------- --------- ------------------------- ---------- -------------------
BIN$1Unhj5+DSHDgNAgAIKds8A==$0 T1                               DROP      TABLE                     8.1832E+12 2004-03-10:11:03:49

SQL> sho user
USER is "SYS"

SQL> SELECT owner,original_name,operation,type
  2  FROM dba_recyclebin
  3  /

OWNER                          ORIGINAL_NAME                    OPERATION TYPE
------------------------------ -------------------------------- --------- ------
BH                             T1                               DROP      TABLE

We can also create a new table with the same name at this point.



PURGING

In order to completely remove the table from the DB and to release the space the new PURGE command is used.

From BH user:
SQL> PURGE TABLE t1;
Table purged.

OR

SQL> PURGE TABLE "BIN$1UtrT/b1ScbgNAgAIKds8A==$0";
Table purged.

From SYSDBA user:
SQL> SELECT owner,original_name,operation,type
  2  FROM dba_recyclebin
  3  /
no rows selected

From BH user:
SQL> SHOW recyclebin
SQL>

 There are various ways to PURGE objects:

PURGE TABLE t1;
PURGE INDEX ind1;
PURGE recyclebin; (Purge all objects in Recyclebin)
PURGE dba_recyclebin; (Purge all objects / only SYSDBA can)
PURGE TABLESPACE users; (Purge all objects of the tablespace)
PURGE TABLESPACE users USER bh; (Purge all objects of the tablspace belonging to BH)

For an object, the owner or a user with SYSDBA privilege or a user with DROP ANY... system privilege for the type of object to be purged can PURGE it.

For more information on the PURGE command refer to the 10g SQL Reference

DISABLING RECYCLEBIN

We can DROP and PURGE a table with a single command

From BH user:
SQL> DROP TABLE t1 PURGE;
Table dropped.

SQL> SELECT *
  2  FROM recyclebin
  3  /
no rows selected

There is no need to PURGE.

On 10gR1, in case we want to disable the behavior of recycling, there is an underscore parameter
"_recyclebin" which defaults to TRUE. We can disable recyclebin by setting it to FALSE.

From SYSDBA user:
SQL> SELECT a.ksppinm, b.ksppstvl, b.ksppstdf
FROM x$ksppi a, x$ksppcv b
WHERE a.indx = b.indx
AND a.ksppinm like '%recycle%'
ORDER BY a.ksppinm
/
         Parameter                            Value                   Default?
---------------------------- ---------------------------------------- --------
_recyclebin                  TRUE                                     TRUE

From BH user:
SQL> CREATE TABLE t1(a NUMBER);
Table created.

SQL> DROP TABLE t1;
Table dropped.

SQL> SELECT original_name
FROM user_recyclebin;
ORIGINAL_NAME
--------------
T1

From SYSDBA user:
SQL> ALTER SYSTEM SET "_recyclebin"=FALSE SCOPE = BOTH;
System altered.

SQL> SELECT a.ksppinm, b.ksppstvl, b.ksppstdf
FROM x$ksppi a, x$ksppcv b
WHERE a.indx = b.indx
AND a.ksppinm like '%recycle%'
ORDER BY a.ksppinm
/
         Parameter                            Value                   Default?
---------------------------- ---------------------------------------- --------
_recyclebin                  FALSE                                     TRUE

From BH user:
SQL> CREATE TABLE t1(a NUMBER);
Table created.

SQL> DROP TABLE t1;
Table dropped.

SQL> SELECT original_name
FROM user_recyclebin;
no rows selected

There is no need to PURGE.

As with anyother underscore parameter, setting this parameter is not recommended unless
advised by oracle support services.

On 10gR2 and higher; recyclebin is a initialization parameter and bydefault its ON.
We can disable recyclebin by using the following commands:

SQL> ALTER SESSION SET recyclebin = OFF;
SQL> ALTER SYSTEM SET recyclebin = OFF;

The dropped objects, when recyclebin was ON will remain in the recyclebin even if we set the recyclebin parameter to OFF.