ORA-55628: Flashback Archive supports Oracle 11g or higher

Today when i am trying to enable flashback data archive on our production box upgraded from 10g to 11gr2 then got below error message

ORA-55628: Flashback Archive supports Oracle 11g or higher

but our database 11gr2 but still i am getting error message becuase compatible parameter was set to 10.1.0.2.0.

SQL> select * from v$version;


BANNER
-----------------------------------------------------------------


Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - Production


PL/SQL Release 11.2.0.2.0 - Production


CORE 11.2.0.2.0 Production


TNS for 32-bit Windows: Version 11.2.0.2.0 - Production


NLSRTL Version 11.2.0.2.0 - Production


SQL> show parameter comp


NAME TYPE VALUE


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


compatible string 10.1.0.2.0




SQL> alter system set compatible = '11.1.0.2.0' scope=spfile;

System altered.



SQL> shutdown immediate


Database closed.


Database dismounted.


ORACLE instance shut down.


SQL> startup


ORACLE instance started.






Total System Global Area 945786880 bytes


Fixed Size 1384328 bytes


Variable Size 729809016 bytes


Database Buffers 209715200 bytes


Redo Buffers 4878336 bytes


Database mounted.


Database opened.