Resource plan managment issue

hi !

i am trying to create a resource group to control the parallel execution of processes.  for this i have created a group and mapped user to it but getting error in creating a plan.

/* create resource group for parallel queries
BEGIN
dbms_resource_manager.clear_pending_area();
dbms_resource_manager.create_pending_area();
dbms_resource_manager.create_consumer_group(consumer_group =>'PARALLEL_GRP',comment =>'resource group for parallel queries');
dbms_resource_manager.submit_pending_area();
END;
/

/* assign users to this group

BEGIN
DBMS_RESOURCE_MANAGER_PRIVS.GRANT_SWITCH_CONSUMER_GROUP ( 'PATRON', 'PARALLEL_GRP', true);
END;
/
OR
exec dbms_resource_manager.set_initial_consumer_group ('PATRON','PARALLEL_GRP');