The ORA-1122 error message isn't enough for me to give you an answer in full. This message should accompany other error messages as well. But what I can tell you about the ORA-1122 error is that one of your database datafiles could not be verified correctly. Without knowing your specific configuration, I would suggest the following steps to try to get your database up and running:
- CONNECT INTERNAL
- STARTUP MOUNT
- RECOVER DATABASE; You should see a message indicating that the database has been recovered.
- ALTER DATABASE OPEN;
If the above does not work, you might have to restore your database from a backup. If you are running in ArchiveLog mode, then you can roll forward all changes since the backup. If you are not running ArchiveLog mode, then you will lose any changes since the last backup.