ORA-00205:error in identifying controlfile

[OracleDoc]

look in the $ORCLE_HOME/dbs folder for the init.ora file and look for the parameter control_files=

This is where the database is expecting to see the control files. Since the error is stating that it can't identify the control file one of 4 things have happened.

1. The init.ora file was altered
2. The control files were deleted
3. The control file is corrupted.
4. The permissions have changed.

The easiest way to fix this is to open up your alert log and see which control file it's complaning about then open your init.ora and look at the control_files parameter, make note of where the database is expecting to see them. Navigate to where that particular control file is suppose to be and see if it's actually there.
If it is it may either be corrupted or permissions have been changed.

You should have more than one control file, (if you don't then you need to ensure you have more in the future).

If do you have more than one control file and the control file that the database is complaining about not seeing is there, check the permissions. If the permissions are right then try re-name that control file to database.ctl_corrupt and copy (not move) one of the others to the location.

If the control file is not there then copy one of the others to the location and rename it to what the init.ora is calling it, then try firing up the database.

If you only have one control file for the database and it's complaining that it can't find it well then you've got another problem to deal with.

Hope I've expanded on the possible cause. Dealing with control files are pretty much cut and dry.