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5-2 Copyright © 2006, Oracle. All rights reserved.
Objectives
After completing this lesson, you should be able to:
• Perform complete or incomplete user-managed recovery
• Identify situations where incomplete recovery is necessary
• Perform complete or incomplete recovery by using RMAN
• Perform incomplete recovery based on time, SCN, log sequence, restore points, or the cancel method
• Recover an automatically backed up control file
• Use Enterprise Manage to perform recovery
• Recover read-only tablespaces
User man.RMAN CLIEMCompleteIncompleteControl fileRO TBS
5-3 Copyright © 2006, Oracle. All rights reserved.
Recovery Methods
There are two methods for performing recovery:
• User-managed recovery– Files must be maintained and moved into place
manually.– Use SQL*Plus commands.
• RMAN recovery– Files are managed automatically.– Use RMAN functionality including all repository
maintenance and reporting capabilities.– This can be done by using Enterprise Manager.– Oracle Corporation recommends using this method.
5-4 Copyright © 2006, Oracle. All rights reserved.
User-Managed Recovery:RECOVER Command
• Restore all database files from a backup and then recover the database:
• Restore the damaged data files from a backup and then recover the data files:
Or:
SQL> RECOVER DATABASE
SQL> RECOVER TABLESPACE index_tbs
SQL> RECOVER DATAFILE 2> '/oradata/indx01.dbf'
5-5 Copyright © 2006, Oracle. All rights reserved.
RMAN Recovery: RESTOREand RECOVER Commands
run{
sql "ALTER TABLESPACE inv_tbs OFFLINE IMMEDIATE";
RESTORE TABLESPACE inv_tbs;
RECOVER TABLESPACE inv_tbs DELETE ARCHIVELOG;
sql "ALTER TABLESPACE inv_tbs ONLINE";
}
User man.> RMAN CLI
EMCompleteIncompleteControl fileRO TBS
5-6 Copyright © 2006, Oracle. All rights reserved.
Recovery UsingEnterprise Manager
With the Enterprise Manager Recovery Wizard, you can create and run an RMAN script to perform the recovery.
RMAN> RECOVER DATABASE …
User man.RMAN CLI
> EMCompleteIncompleteControl fileRO TBS
5-7 Copyright © 2006, Oracle. All rights reserved.
Complete Versus Incomplete Recovery
There are two types of recovery:
• Complete recovery brings the database up to the present, including all data changes made to the point in time when the recovery was requested.
• Incomplete recovery brings the database up to a specified point in time in the past, before the recovery operation was requested.
Recoverytask startedat this time
Completerecovery
Incompleterecovery
Missing transactionsafter incomplete recovery
Restore fromthis backup
5-8 Copyright © 2006, Oracle. All rights reserved.
Complete Recovery
Restoreddata files
Data files containingcommitted anduncommittedtransactions
Recovereddata files
Changes applied
Undo applied
6
5
3
2
1
Archivedlog Archived
log OnlineRedo log
User man.RMAN CLIEM
> CompleteIncompleteControl fileRO TBS
4
Databaseopened
5-9 Copyright © 2006, Oracle. All rights reserved.
Incomplete Recovery
Data files containingcommitted anduncommitted
Transactions up to PIT
PIT-recovereddata files
Undo applied
6
5
3
2
1
Archivedlog Archived
log OnlineRedo log
4
Databaseopened
XX
Changes applied to point in time (PIT)
Restored datafiles from as far
back as necessary
User man.RMAN CLIEMComplete
> IncompleteControl fileRO TBS
5-11 Copyright © 2006, Oracle. All rights reserved.
Situations Requiring Incomplete Recovery
• Complete recovery fails because of a missing archived log file.
• One or more unarchived redo log files and a data file are lost.
• A backup of the control file is used to open or recover the database.
5-12 Copyright © 2006, Oracle. All rights reserved.
Types of Incomplete Recovery
There are four types of incomplete recovery:
• Time-based recovery
• Cancel-based recovery
• Change-based recovery
• Log sequence recovery
5-14 Copyright © 2006, Oracle. All rights reserved.
Performing User-ManagedIncomplete Recovery
• Recover a database until time:
• Recover a database until cancel:
• Recover using the backup control file:
SQL> RECOVER DATABASE UNTIL CANCEL;
SQL> RECOVER DATABASE UNTIL
2 TIME '2005-12-14:12:10:03';
SQL> RECOVER DATABASE 2 UNTIL TIME '2005-12-14:12:10:03' 3 USING BACKUP CONTROLFILE;
5-15 Copyright © 2006, Oracle. All rights reserved.
Performing User-Managed Incomplete Recovery
To perform user-managed incomplete recovery, follow these steps:
1. Shut down the database.
2. Restore data files.
3. Mount the database.
4. Recover the database.
5. Open the database with the RESETLOGS option.
5-16 Copyright © 2006, Oracle. All rights reserved.
User-Managed Time-Based Recovery: Example
SQL> SHUTDOWN IMMEDIATE$ cp /BACKUP/* /u01/db01/ORADATASQL> STARTUP MOUNTSQL> RECOVER DATABASE UNTIL TIME '2005-11-28:11:44:00';SQL> ALTER DATABASE OPEN RESETLOGS;
This is the scenario:
• A job ran in error, and its effects have to be undone.
• This happened 15 minutes ago, and there has been little database activity since then.
• You decide to perform incomplete recovery to restore the database back to its state as of 15 minutes ago.
5-18 Copyright © 2006, Oracle. All rights reserved.
User-Managed Cancel-Based Recovery: Example
The scenario is the same as the one for the time-based example, except for these findings:
• Redo logs are not multiplexed.
• One of the online redo logs is missing.
• The missing redo log is not archived.
• The redo log contained information from 11:34 a.m.
• Twenty-six minutes of data are lost.
• Users can reenter their data manually.
5-19 Copyright © 2006, Oracle. All rights reserved.
User-Managed Cancel-Based Recovery: Example
Recover the database as follows:
1. Shut down the database.
2. Restore all data files from the most recent backup.
3. You already have a valid backup, so mount the database.
4. Execute RECOVER DATABASE UNTIL CANCEL.
5. Execute ALTER DATABASE OPEN RESETLOGS to open the database.
5-20 Copyright © 2006, Oracle. All rights reserved.
Performing Incomplete Recoveryby Using RMAN
1. Mount the database.
2. Allocate multiple channels for parallelization.
3. Restore all data files.
4. Recover the database by using UNTIL TIME, UNTIL SEQUENCE, or UNTIL SCN.
5. Open the database by using RESETLOGS.
5-21 Copyright © 2006, Oracle. All rights reserved.
Time-Based RecoveryUsing RMAN: Example
RMAN> RUN {
2> SET UNTIL TIME = '2005-11-28:11:44:00';
3> RESTORE DATABASE;
4> RECOVER DATABASE;
5> ALTER DATABASE OPEN RESETLOGS; }
5-23 Copyright © 2006, Oracle. All rights reserved.
Log Sequence RecoveryUsing RMAN: Example
RMAN> RUN { 2> SET UNTIL SEQUENCE 120 THREAD 1; 3> ALTER DATABASE MOUNT; 4> RESTORE DATABASE; 5> RECOVER DATABASE; # recovers through log 119 6> ALTER DATABASE OPEN RESETLOGS; 7> }
5-25 Copyright © 2006, Oracle. All rights reserved.
Incomplete Recovery and the Alert Log
The following are some best practices regarding the alert log in incomplete recovery scenarios:
• Check the alert log before and after recovery.
• Look for error information, hints, and SCNs.
• Confirm that steps in the recovery process were successful.
5-26 Copyright © 2006, Oracle. All rights reserved.
Restore Points
A restore point:
• Serves as an alias for anSCN or a specific point in time
• Is stored in the control file
• Can be used with:– RECOVER DATABASE– FLASHBACK DATABASE– FLASHBACK TABLE
SQL> CREATE RESTORE POINT before_load;
before_load
RMAN> RECOVER DATABASE UNTIL RESTORE POINT before_load;2
1
5-27 Copyright © 2006, Oracle. All rights reserved.
Incomplete Recovery: Best Practices
• Plan for and practice scenarios ahead of time.
• Investigate and verify that incomplete recovery is necessary.
• Follow all steps carefully.
• Take whole database backups before and after recovery.
• Always verify that the recovery was successful.
• Take advantage of restore points.
5-29 Copyright © 2006, Oracle. All rights reserved.
Recovering a Control FileAutobackup
RecoveryManager(RMAN) Flash recovery
area
Database
Controlfile
RECOVER DATABASE;
ALTER DATABASE OPEN RESETLOGS;
ALTER TABLESPACE temp ADD TEMPFILE...;
RMAN> RESTORE CONTROLFILE TO 2> '/oradata/ctlfile.bak' FROM AUTOBACKUP;
User man.RMAN CLIEMCompleteIncomplete
> Control fileRO TBS
5-31 Copyright © 2006, Oracle. All rights reserved.
Creating a New Control File
SQL> ALTER DATABASE BACKUP CONTROLFILE TO TRACE;
Passwordfile
Parameter file
SYSTEM
SYSAUX
UNDO TEMP
USERS
INDEX
Redo logfile 1B
Redo logfile 1A
Redo logfile 2B
Redo logfile 2A
Controlfiles
5-33 Copyright © 2006, Oracle. All rights reserved.
Recovering Read-OnlyTablespaces
ChangeTablespace
State
Crashand perform
recovery
Case 1
Case 2
Case 3
Backup
Read-only
Read/write
Read-only
Read-only
Read/write
*
*
*
* Control filebackup to be
used for recoveryif current one lost
User man.RMAN CLIEMCompleteIncompleteControl file
> RO TBS
5-35 Copyright © 2006, Oracle. All rights reserved.
Read-Only Tablespace Recovery Issues
Special considerations must be taken for read-onlytablespaces when:
• Re-creating a control file
• Renaming data files
• Using a backup control file
5-37 Copyright © 2006, Oracle. All rights reserved.
Summary
In this lesson, you should have learned how to:
• Perform complete or incomplete user-managed recovery
• Perform complete or incomplete recovery by using RMAN
• Identify situations where incomplete recovery is necessary
• Perform incomplete recovery based on time, SCN, log sequence, restore points, or the cancel method
• Recover a control file autobackup
• Use Enterprise Manage to perform recovery
• Recover read-only tablespaces