Oracle7 Server Administrator's Guide
Performing Complete Media Recovery
This section describes the steps necessary to complete media recovery operations, and includes the following topics:
Do not depend solely on the steps in the following procedures to understand all the tasks necessary to recover from a media failure. If you haven't already done so, familiarize yourself with the fundamental recovery concepts and strategies ![[*]](jump.gif)
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See Also: See for a detailed list of the different problems that media failures can cause and describes the appropriate methods of recovery from each type of problem.
Performing Closed Database Recovery
This section describes steps to perform closed database recovery of either all damaged datafiles in one operation, or individual recovery of each damaged datafile in separate operations.
To Perform Closed Database Recovery
1. If the database is open, shut it down using the Server Manager Shutdown Abort mode of the Shutdown Database dialog box, or the SHUTDOWN command with the ABORT option.
2. If you're recovering from a media error, correct it if possible.
Attention: If the hardware problem that caused the media failure was temporary, and the data was undamaged (for example, a disk or controller power failure), stop at this point.
3. If files are permanently damaged, restore the most recent backup files (taken as part of a full or partial backup) of only the datafiles damaged by the media failure. Do not restore any undamaged datafiles or any online redo log files. If the hardware problem has been repaired, and damaged datafiles can be restored to their original locations, do so, and skip Step 6 of this procedure. If the hardware problem persists, restore the datafiles to an alternative storage device of the database server and continue with this procedure.
Note: If you do not have a backup of a specific datafile, you might be able to create an empty replacement file that can be recovered.
4. Start Server Manager and connect to Oracle with administrator privileges.
5. Start a new instance and mount, but do not open, the database using either the Server Manager Startup Database dialog box (with the Startup Mount radio button selected), or the STARTUP command with the MOUNT option.
6. If one or more damaged datafiles were restored to alternative locations in Step 3, the new location of these files must be indicated to the control file of the associated database. Therefore, use the operation described in "Renaming and Relocating Datafiles" , as necessary.
7. All datafiles you want to recover must be online during complete media recovery. To get the datafile names, check the list of datafiles that normally accompanies the current control file, or query the V$DATAFILE view. Then, issue the ALTER DATABASE command with the DATAFILE ONLINE option to ensure that all datafiles of the database are online. For example, to guarantee that a datafile named USERS1 (a fully specified filename) is online, enter the following statement:
ALTER DATABASE DATAFILE 'users1' ONLINE;
If a specified datafile is already online, Oracle ignores the statement.
8. To start closed database recovery of all damaged datafiles in one step, use either the Server Manager Apply Recovery Archive dialog box, or an equivalent RECOVER DATABASE statement.
- 8.1 To start closed database recovery of an individual damaged datafile, use the RECOVER DATAFILE statement in Server Manager.
Note: For maximum performance, use parallel recovery to recover the datafiles.
9. Now Oracle begins the roll forward phase of media recovery by applying the necessary redo log files (archived and online) to reconstruct the restored datafiles. Unless the application of files is automated, Oracle prompts you for each required redo log file.
Oracle continues until all required archived redo log files have been applied to the restored datafiles. The online redo log files are then automatically applied to the restored datafiles and notifies you when media recovery is complete. If no archived redo log files are required for complete media recovery, Oracle does not prompt for any. Instead, all necessary online redo log files are applied, and media recovery is complete.
After performing closed database recovery, the database is recovered up to the moment that media failure occurred. You can then open the database using the SQL command ALTER DATABASE with the OPEN option.
See Also: See "Restoring Damaged Datafiles" for more information about creating datafiles.
For more information about datafile lists, see "Listing Database Files Before Backup" .
For more information about applying redo log files, see "Applying Redo Log Files" .
Performing Open-Database, Offline-Tablespace Recovery
At this point, an open database has experienced a media failure, and the database remains open while the undamaged datafiles remain online and available for use. The damaged datafiles are automatically taken offline by Oracle.
This procedure cannot be used to perform complete media recovery on the datafiles of the SYSTEM tablespace. If the media failure damages any datafiles of the SYSTEM tablespace, Oracle automatically shuts down the database.
See Also: To proceed with complete media recovery, follow the procedure in "Performing Closed Database Recovery" .
To Perform Open-Database, Offline-Tablespace Recovery
1. The starting point for this recovery operation can vary, depending on whether you left the database open after the media failure occurred.
- 1.1 If the database was shut down, start a new instance, and mount and open the database. Perform this operation using the Server Manager Startup Database dialog box (with the Startup Open radio button selected), or with the STARTUP command with the OPEN option. After the database is open, take all tablespaces that contain damaged datafiles offline.
- 1.2 If the database is still open and only damaged datafiles of the database are offline, take all tablespaces containing damaged datafiles offline. Oracle identifies damaged datafiles via error messages. Tablespaces can be taken offline using either the Take Offline menu item of Server Manager, or the SQL command ALTER TABLESPACE with the OFFLINE option, as described in "Taking Tablespaces Offline" . If possible, take the damaged tablespaces offline with temporary priority (to minimize the amount of recovery).
2. Correct the hardware problem that caused the media failure. If the hardware problem cannot be repaired quickly, you can proceed with database recovery by restoring damaged files to an alternative storage device.
3. If files are permanently damaged, restore the most recent backup files (taken as part of a full or partial backup) of only the datafiles damaged by the media failure. Do not restore undamaged datafiles, online redo log files, or control files. If the hardware problem has been repaired and the datafiles can be restored to their original locations, do so. If the hardware problem persists, restore the datafiles to an alternative storage device of the database server.
Note: If you do not have a backup of a specific datafile, you can create an empty replacement file, which can be recovered.
4. If one or more damaged datafiles were restored to alternative locations (Step 3), indicate the new locations of these files to the control file of the associated database by using the procedure in "Renaming and Relocating Datafiles" , as necessary.
5. After connecting with administrator privileges, use the RECOVER TABLESPACE statement in Server Manager to start offline tablespace recovery of all damaged datafiles in one or more offline tablespaces using one step.
Note: For maximum performance, use parallel recovery to recover the datafiles.
6. Oracle begins the roll forward phase of media recovery by applying the necessary redo log files (archived and online) to reconstruct the restored datafiles. Unless the applying of files is automated, Oracle prompts for each required redo log file.
If no archived redo log files are required for complete media recovery, Oracle does not prompt for any. Instead, all necessary online redo log files are applied, and media recovery is complete.
7. The damaged tablespaces of the open database are now recovered up to the moment that media failure occurred. You can bring the offline tablespaces online using the Place Online menu item of Server Manager, or the SQL command ALTER TABLESPACE with the ONLINE option.
See Also: For more information about redo log application, see "Applying Redo Log Files" .
For more information about creating datafiles, see "Restoring Damaged Datafiles" .
Performing Open-Database, Offline-Tablespace Individual Recovery
Identical to the preceding operation, here an open database has experienced a media failure, and remains open while the undamaged datafiles remain online and available for use. The damaged datafiles are automatically taken offline by Oracle.
Note: This procedure cannot be used to perform complete media recovery on the datafiles of the SYSTEM tablespace. If the media failure damages any datafiles of the SYSTEM tablespace, Oracle automatically shuts down the database.
To Perform Open-Database, Offline-Tablespace Individual Recovery
1. The starting point for this recovery operation can vary, depending on whether you left the database open after the media failure occurred.
- 1.1 If the database was shut down, start a new instance, and mount and open the database. Perform this operation using the Server Manager Startup Database dialog box (with the Startup Open radio button selected), or with the STARTUP command with the OPEN option. After the database is open, take all tablespaces that contain damaged datafiles offline.
- 1.2 If the database is still open and only damaged datafiles of the database are offline, take all tablespaces containing damaged datafiles offline. Oracle identifies damaged datafiles via error messages. Tablespaces can be taken offline using either the Take Offline menu item of Server Manager, or the SQL command ALTER TABLESPACE with the OFFLINE option, as described in "Taking Tablespaces Offline" . If possible, take the damaged tablespaces offline with temporary priority (to minimize the amount of recovery).
2. Correct the hardware problem that caused the media failure. If the hardware problem cannot be repaired quickly, you can proceed with database recovery by restoring damaged files to an alternative storage device.
3. If files are permanently damaged, restore the most recent backup files (taken as part of a full or partial backup) of only the datafiles damaged by the media failure. Do not restore undamaged datafiles, online redo log files, or control files. If the hardware problem has been repaired and the datafiles can be restored to their original locations, do so. If the hardware problem persists, restore the datafiles to an alternative storage device of the database server.
Note: If you do not have a backup of a specific datafile, you can create an empty replacement file, which can be recovered.
4. If one or more damaged datafiles were restored to alternative locations (Step 3), indicate the new locations of these files to the control file of the associated database by using the procedure in "Renaming and Relocating Datafiles" , as necessary.
5. After connecting with administrator privileges use the RECOVER DATAFILE statement in Server Manager to start recovery of an individual damaged datafile in an offline tablespace
Note: For maximum performance, use parallel recovery to recover the datafiles.
6. Oracle begins the roll forward phase of media recovery by applying the necessary redo log files (archived and online) to reconstruct the restored datafiles. Unless the application of files is automated, Oracle prompts for each required redo log file.
If no archived redo log files are required for complete media recovery, Oracle does not prompt for any. Instead, all necessary online redo log files are applied, and media recovery is complete.
7. The damaged tablespaces of the open database are now recovered up to the moment that media failure occurred. You can bring the offline tablespaces online using the Place Online menu item of Server Manager, or the SQL command ALTER TABLESPACE with the ONLINE option.
See Also: For information about how to proceed with complete media recovery, see "Performing Closed Database Recovery" .
For more information about creating datafiles, see "Restoring Damaged Datafiles" .