| ERROR | WARNING: Files may exist in string that are not known to database. |
| CAUSE | One of the following events caused this: 1. A database crash happened during file creation. 2. A backup control file was restored. 3. The control file was re-created. 4. DB_RECOVERY_FILE_DEST has previously been enabled and then disabled. |
| ACTION | Use RMAN command CATALOG RECOVERY AREA to re-catalog any such files. If the file header is corrupted, then delete those files using an OS utility. Do not use messages 19817; it is used for simulating lock failure Do not use messages 19818; it is used for space reclamation before backup Do not use messages 19819; it is used to disable clearing file name |