ORA-00205: Error in identifying control file, check alert log for more info
What causes this error?
An ORA-00205 error occurs when the system cannot find the control file. The filename and the size of the file do not match the list of the control files that it holds.
How to fix it
If the system can't find the control file, then the database can't be mounted. Find the file and put it in the path, as specified in the SPFILE/INITSID.ORA file's CONTROL_FILES parameter else check the CONTROL_FILES parameter of the SPFILE/INITSID.ORA file. Check if you have referenced the correct file.
You can find this by executing:
SHOW PARAMETERS control_files
SELECT VALUE FROM V$PARAMETER WHERE NAME = 'control_files' /
Check that ALL controlfiles, found using the select above, are online and that they are the same files that the system created at cold start time.
If you cannot find the control file, then start the instance without mounting the database and use the CREATE CONTROLFILE statement to create a new control file. After creating the control file, shut the database. Now add this control file to the SPFILE/INIT.ORA and then start the database.