16655, 0000, "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: 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,
fast-start failover may be disabled. Then retry the command
using the originally specified target standby database.