Oracle Message ORA-16644 - apply instance not available

ERRORapply instance not available
CAUSEThe broker operation could not finish, because it requires a running apply instance for the standby database, and either there was no such instance designated for the standby database or the designated apply instance was not currently available.
ACTIONStart the designated apply instance or wait until the broker specifies an instance to be the apply instance and reissue the command.