A standby control file essentially keeps the same information of the primary database with the control file, which is the physical structure of the database. It also contains some specific information about the Data Guard, such as whether an archive log sequence is applied or not. A standby control file is mandatory to mount a physical standby database, and we should consider keeping multiple copies of the standby control file, preferably on different disks, which is known as multiplexing.
In some cases, we may want to renew a standby control file by using a newly created one on the primary database. For example, before a switchover it's a good practice to renew the standby control file in order to guarantee that all of the redo, temp file structure, and historical archived log data are the same. In general, this is a three-step operation:
Create a copy of the standby control file from the primary database.
Transfer this standby control file from the primary...