SQL> alter system set shared_servers=3;
alter system set shared_servers=3
*
ERROR at line 1:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-00120: dispatching mechanism not enabled or installed


SQL> alter system set shared_servers=3 scope=spfile;

System altered.

SQL> alter system set dispatchers='(PROTOCOL=TCP)(DISP=3)' scope=spfile;
alter system set dispatchers='(PROTOCOL=TCP)(DISP=3)' scope=spfile
*
ERROR at line 1:
ORA-02065: illegal option for ALTER SYSTEM


SQL> alter system set dispatchers='(PROTOCOL=TCP)(DISP=3)';
alter system set dispatchers='(PROTOCOL=TCP)(DISP=3)'
*
ERROR at line 1:
ORA-00105: dispatching mechanism not configured for network protocol
(ADDRESS=(PARTIAL=YES)(PROTOCOL=TCP))


SQL> alter system set dispatchers='(PROTOCOL=TCP)(DISP=2)';
alter system set dispatchers='(PROTOCOL=TCP)(DISP=2)'
*
ERROR at line 1:
ORA-00105: dispatching mechanism not configured for network protocol
(ADDRESS=(PARTIAL=YES)(PROTOCOL=TCP))


SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORA-00121: SHARED_SERVERS specified without DISPATCHERS

Do anybody have idea about it?
Thanx in Advance