Mirroring the Control File


It is essential to mirror the control file in your Oracle database.

If you only have one copy of the control file and lose this copy due to a disk error or other problems, it is probably impossible to completely recover the database. The result is inevitable data loss.

To prevent this happening, create multiple copies of the control file. When the SAP 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.


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.


If necessary, change the standard mirroring of the control file by setting the control_filesparameter.

Here is a 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/C11/102_64).