Mirroring the Control File 

Use

If you only have one copy of the control file and lose this copy due to a disk error or other problems, it will likely be impossible to completely recover the database. This means data loss will be inevitable. To protect your database against the loss of the control file, create multiple copies. When the R/3 System is installed, the control file is mirrored to at least two additional disks (often three). You can also mirror the control file yourself; always make sure that all the control files are on different disks.

Prerequisites

The default database profile (init<DBSID>.ora profile) delivered with the system makes sure that the control file and its mirror copies are stored in directories that are mounted on different disks.

Procedure

You can change the standard mirroring of the control file by setting the control_files parameter.

Sample entry in profile init<DBSID>.ora:

control_files = (?/dbs/cntrl<SAPSID>.dbf, ?/sapdata1/cntrl/ctrl<SAPSID>.dbf,?/sapdata2/cntrl/ctrl<SAPSID>.dbf)

The question mark ? is the official Oracle placeholder for the home directory of the database system (for example, /oracle/C11).