Applying slowly on the physical standby RAC.

  Hi all, 

   I setup Data Guard (version 11.1) successfull ! My primary database is RAC and two physical standby databases (RAC and single). Applying redo data from primary to two physical standby database is OK but applying on physical standby single database is quickly than physical standby RAC. On standby RAC slowly and sometime not apply, I must restart instances and apply service (I use Real-Time aplly). I know at a time, only one instance apply data, I use:

select process, thread#, sequence#, status from v$managed_standby where process='MRP0';

--> MRP0 only exist on instance 1 not 2.

I think that standby RAC database should active one instance maybe solve applying slowly ! But Data Guard is production so I can not test with this idea ! Take me some comment about this problem !