Administering Oracle Real Application Clusters

 
The Server Control (SRVCTL) utility  allows  you to start and stop database and instances, manage configuration information, move or remove instances and services.
Allows you to reallocate a service from one named instance to another named instance; the relocated service is temporary until you modify the configuration.
An example:
Problem:
We need to redistribute existing services.
Solution:
We can implement  it  by dropping the existing service and re-creating it.
This implies a reboot of our application server and the possibility of errors.. .  Not good.
 
srvctl modify service gives us the possibility of redefine the service without need of re-creating it or even stopping it.  Good.
command sintax :
srvctl relocate service -d mndb -s mndb_sales -i mndb1 -t mndb2
-d db_unique_name:Unique name for the database.
-s service_name:Service name.
-i old_inst_name:Old instance name.
-t new_inst_name:New instance name.
-f Disconnect all sessions during stop or relocate service operations.