Overview

In order to fix that, we have to:

Mount the database (if it is down, although shouldn't be)

Clear the logfile groups

Open the database normally

Mount

Now, firstly, to mount the database we have to have:

Parameter file(pfile or SPFILE)

Control file (Binary, NOT SQL commands)

If we have these two files, we can mount ANY database regardless if we have or don't have: datafiles, redo log files or whatever. S

Clear log files

Once we have the database mounted, we can check if all the files are correct and the header isn't corrupted:

So once they have been fixed, we can proceed with the clearing:

Monitor the alert log, just to be sure that all is fine. Once the database opens, please switch couple times to guarantee consistency and that all mechanisms are working.