Oracle Database 10g Enterprise Edition Release 10.1.0.2.0 - Prod
PL/SQL Release 10.1.0.2.0 - Production
CORE    10.1.0.2.0      Production
TNS for 32-bit Windows: Version 10.1.0.2.0 - Production
NLSRTL Version 10.1.0.2.0 - Production

scott@orcl> create table flashdrop as 
  2  select * from user_tables 
  3  where rownum < 6;

Table created.

scott@orcl> show recyclebin
scott@orcl> drop table flashdrop;

Table dropped.

scott@orcl> show recyclebin
ORIGINAL NAME    RECYCLEBIN NAME                OBJECT TYPE  DROP TIME
---------------- ------------------------------ ------------ -------------------
FLASHDROP        BIN$rcmdDvJ9RNir/0FA7jcZfw==$0 TABLE        2009-05-05:10:56:01
scott@orcl> alter session set recyclebin=OFF;
alter session set recyclebin=OFF
                  *
ERROR at line 1:
ORA-02248: invalid option for ALTER SESSION 

ALTER SESSION SET RECYCLEBIN=OFF

SQL> select object_name, original_name, type, can_undrop as "UND", can_purge as "PUR",
  2   droptime, base_object, purge_object
  3  from recyclebin
  4  order by droptime;

OBJECT_NAME                    ORIGINAL_NAME TYPE  UND PUR DROPTIME            BASE_OBJECT PURGE_OBJECT
------------------------------ ------------- ----- --- --- ------------------- ----------- ------------
BIN$HGnc56ACrRPgQPeM/qQoRw==$0 TST           TABLE YES YES 2006-09-01:16:34:12      233031       233031

SQL> alter session set recyclebin=off ;

Session altered.

SQL> create table tst (col varchar2(10), row_chng_dt date);

Table created.

SQL> insert into tst values ('Version5', sysdate);

1 row created.

SQL> drop table tst ;

Table dropped.

SQL> select object_name, original_name, type, can_undrop as "UND", can_purge as "PUR",
  2   droptime, base_object, purge_object
  3  from recyclebin
  4  order by droptime;

OBJECT_NAME                    ORIGINAL_NAME   TYPE UND PUR DROPTIME            BASE_OBJECT PURGE_OBJECT
------------------------------ -------------- ----- --- --- ------------------- ----------- ------------
BIN$HGnc56ACrRPgQPeM/qQoRw==$0 TST            TABLE YES YES 2006-09-01:16:34:12      233031       233031