ORA-16655: specified target standby database invalid
Cause : The attempted command was not allowed because Fast-Start Failover was enabled for this Data Guard configuration and the target standby database specified in the command differs from the standby database that was indicated by the FastStartFailoverTarget property associated with the current primary database.
Action - How to fix it : DBA Scripts :: www.high-oracle.com/scripts
Retry the attempted command by specifying the standby database that is indicated by the FastStartFailoverTarget property that is associated with the current primary database. Alternatively, you may disable Fast-Start Failover. You may then retry the command while specifying the originally specified target standby database.
Well, the reason for above error is that i have taken the above script from a 11g database and running it on 10g database. 11g has bring some changes in password management. Below code is executed on 11g and user created successfully, which is expected result.