18 Performing Flashback and Database Point-in-Time Recovery

Typically, the following situations call for flashback features or point-in-time recovery:

• A user error or corruption removes needed data or introduces corrupted data. For example, a user or DBA might erroneously delete or update the contents of one or more tables, drop database objects that are still needed during an update to an application, or run a large batch update that fails midway.

• A database upgrade fails or an upgrade script goes awry.

• A complete database recovery after a media failure cannot succeed because you do not have all of the needed redo logs or incremental backups.

In these situations, you can use point-in-time recovery or flashback features to return the database or database object to its state at a previous point in time.

The most basic solution to unwanted database changes is RMAN database point-in-time recovery (DBPITR). DBPITR is sometimes called incomplete recovery because it does not use all of the available redo or completely recover all changes to your database. In this case, you restore a whole database backup and then apply redo logs or incremental backups to re-create all changes up to a point in time before the unwanted change.

If unwanted database changes are extensive but confined to specific tablespaces, then you can use tablespace point-in-time recovery (TSPITR) to return these tablespaces to an earlier system change number (SCN) while the unaffected tablespaces remain available. RMAN TSPITR is an advanced technique described in Performing RMAN Tablespace Point-in-Time Recovery (TSPITR) .

If unwanted database changes are limited to specific tables or table partitions, then you can use a previously created RMAN backup to return only these objects to a point in time before the unwanted changes occurred. Recovering tables or table partitions to a specific point in time is described in Recovering Tables and Table Partitions from RMAN Backups.

Oracle Database also provides a set of features collectively known as Flashback Technology that supports viewing past states of data, and winding and rewinding data back and forth in time, without requiring the restore of the database from backup. Depending on the changes to your database, Flashback Technology can often reverse the unwanted changes more quickly and with less impact on database availability.

To use the Flashback Table feature on one or more tables, use the FLASHBACK TABLE SQL statement with a target time or SCN.

You must have the following privileges to use the Flashback Table feature:

• You must have been granted the FLASHBACK ANY TABLE system privilege or you must have the FLASHBACK object privilege on the table.

• You must have READ or SELECT, INSERT, DELETE, and ALTER privileges on the table.

• To flash back a table to a restore point, you must have the SELECT ANY DICTIONARY or FLASHBACK ANY TABLE system privilege or the SELECT_CATALOG_ROLE role.

For an object to be eligible to be flashed back, the following prerequisites must be met:

• The object must not be included the following categories: tables that are part of a cluster, materialized views, Advanced Queuing (AQ) tables, static data dictionary tables, system tables, remote tables, object tables, nested tables, or individual table partitions or subpartitions.

• The structure of the table must not have been changed between the current time and the target flashback time.

  The following Data Definition Language (DDL) operations change the structure of a table: upgrading, moving, or truncating a table; adding a constraint to a table, adding a table to a cluster; modifying or dropping a column; adding, dropping, merging, splitting, coalescing, or truncating a partition or subpartition (except adding a range partition).

• Row movement must be enabled on the table, which indicates that rowids change after the flashback occurs.

  This restriction exists because if rowids before the flashback were stored by the application, then there is no guarantee that the rowids correspond to the same rows after the flashback. If your application depends on rowids, then you cannot use Flashback Table.

• The undo data in the undo tablespace must extend far enough back in time to satisfy the flashback target time or SCN.

  The point to which you can perform Flashback Table is determined by the undo retention period, which is the minimal time for which undo data is kept before being recycled, and tablespace characteristics. The undo data contains information about data blocks before they were changed. The flashback operation uses undo to re-create the original data.

  To ensure that the undo information is retained for Flashback Table operations, Oracle suggests setting the UNDO_RETENTION parameter to 86400 seconds (24 hours) or greater for the undo tablespace.

1. Ensure that the prerequisites described in Prerequisites for Flashback Table are met.
2. Connect SQL*Plus to the target database and identify the current SCN.

   You cannot roll back a FLASHBACK TABLE statement, but you can issue another FLASHBACK TABLE statement and specify a time just before the current time. Therefore, it is advisable to record the current SCN. You can obtain it by querying V$DATABASE as follows:

   SELECT CURRENT_SCN FROM V$DATABASE;
   

3. Identify the time, SCN, or restore point to which you want to return the table.

   If you have created restore points, then you can list available restore points by executing the following query:

   SELECT NAME, SCN, TIME FROM V$RESTORE_POINT;
   

4. Ensure that enough undo data exists to rewind the table to the specified target.

   If the UNDO_RETENTION intialization parameter is set, and the undo retention guarantee is on, then you can use the following query to determine how long undo data is being retained:

   SELECT NAME, VALUE/60 MINUTES_RETAINED
   FROM   V$PARAMETER
   WHERE  NAME = 'undo_retention';
   

5. Ensure that row movement is enabled for all objects that you are rewinding with Flashback Table.

   You can enable row movement for a table with the following SQL statement, where table is the name of the table that you are rewinding:

   ALTER TABLE table ENABLE ROW MOVEMENT;
   

6. Determine whether the table that you intend to flash back has dependencies on other tables. If dependencies exist, then decide whether to flash back these tables as well.

   You can issue the following SQL query to determine the dependencies, where schema_name is the schema for the table to be flashed back and table_name is the name of the table:

   SELECT other.owner, other.table_name
   FROM   sys.all_constraints this, sys.all_constraints other
   WHERE  this.owner = schema_name
   AND    this.table_name = table_name
   AND    this.r_owner = other.owner
   AND    this.r_constraint_name = other.constraint_name
   AND    this.constraint_type='R';
   

7. Execute a FLASHBACK TABLE statement for the objects to flash back.

   The following SQL statement returns the hr.temp_employees table to the restore point named temp_employees_update:

   FLASHBACK TABLE hr.temp_employees
     TO RESTORE POINT temp_employees_update;
   

   The following SQL statement rewinds the hr.temp_employees table to its state when the database was at the time specified by the SCN:

   FLASHBACK TABLE hr.temp_employees
     TO SCN 123456;
   

   As shown in the following example, you can also specify the target point in time with TO_TIMESTAMP:

   FLASHBACK TABLE hr.temp_employees
     TO TIMESTAMP TO_TIMESTAMP('2013-10-17 09:30:00', 'YYYY-MM-DD HH:MI:SS');
   

   Note:

   The mapping of time stamps to SCNs is not always exact. When you use time stamps with the FLASHBACK TABLE statement, the time to which the table is flashed back can vary by up to approximately 3 seconds of the time specified for TO_TIMESTAMP. If an exact point in time is required, then use an SCN rather than a time.

8. Optionally, query the table to check the data.

Flashback Drop reverses the effects of a DROP TABLE operation. Flashback Drop is faster than other recovery mechanisms that can be used in this situation, such as point-in-time recovery, and does not lead to downtime or loss of recent transactions.

When you drop a table, the database does not immediately remove the space associated with the table. Instead, the table is renamed and, along with any associated objects, placed in the recycle bin. System-generated recycle bin object names are unique. You can query objects in the recycle bin, just as you can query other objects.

A flashback operation retrieves the table from the recycle bin. When retrieving dropped tables, you can specify either the original user-specified name of the table or the system-generated name.

When you drop a table, the table and all of its dependent objects go into the recycle bin together. Likewise, when you perform Flashback Drop, the objects are generally all retrieved together. When you restore a table from the recycle bin, dependent objects such as indexes do not get their original names back; they retain their system-generated recycle bin names. Oracle Database retrieves all indexes defined on the table except for bitmap join indexes, and all triggers and constraints defined on the table except for referential integrity constraints that reference other tables.

Some dependent objects such as indexes may possibly have been reclaimed because of space pressure. In such cases, the reclaimed dependent objects are not retrievable from the recycle bin.

The following list summarizes the user privileges required for the operations related to Flashback Drop and the recycle bin:

• DROP

  Any user with DROP privileges over an object can drop the object, placing it in the recycle bin.

• FLASHBACK TABLE ... TO BEFORE DROP

  Privileges for this statement are tied to the privileges for DROP. That is, any user who can drop an object can perform Flashback Drop to retrieve the dropped object from the recycle bin.

• PURGE

  Privileges for a purge of the recycle bin are tied to the DROP privileges. Any user having DROP TABLE, DROP ANY TABLE, or PURGE DBA_RECYCLE_BIN privileges can purge the objects from the recycle bin.

• READ or SELECT and FLASHBACK for objects in the Recycle Bin

  Users must have the READ or SELECT and FLASHBACK privileges over an object in the recycle bin to query the object in the recycle bin. Any users who had the READ or SELECT privilege over an object before it was dropped continue to have the READ or SELECT privilege over the object in the recycle bin. Users must have FLASHBACK privilege to query any object in the recycle bin, because these are objects from a past state of the database.

Objects must meet the following prerequisites to be eligible for retrieval from the recycle bin:

• The recycle bin is only available for non-system, locally managed tablespaces. If a table is in a non-system, locally managed tablespace, but one or more of its dependent segments (objects) is in a dictionary-managed tablespace, then these objects are protected by the recycle bin.

• Tables that have fine-grained auditing (FGA) and Virtual Private Database (VPD) policies defined over them are not protected by the recycle bin.

• Partitioned index-organized tables are not protected by the recycle bin.

• The table must not have been purged, either by a user or by Oracle Database during a space reclamation operation.

1. Ensure that the prerequisites described in Prerequisites of Flashback Drop are met.
2. Connect SQL*Plus to the target database and obtain the name of the dropped table in the recycle bin.

   You can use the SQL*Plus command SHOW RECYCLEBIN as follows:

   SHOW RECYCLEBIN;
   
   ORIGINAL NAME    RECYCLEBIN NAME                   TYPE         DROP TIME
   ---------------- --------------------------------- ------------ -------------
   EMPLOYEE_DEMO    BIN$gk3lsj/3akk5hg3j2lkl5j3d==$0  TABLE    2013-04-11:17:08:54
   

   The ORIGINAL NAME column shows the original name of the object, whereas the RECYCLEBIN NAME column shows the name of the object as it exists in the bin.

   Alternatively, you can query USER_RECYCLEBIN or DBA_RECYCLEBIN to obtain the table name. The following example queries the RECYCLEBIN view to determine the original names of dropped objects:

   SELECT object_name AS recycle_name, original_name, type 
   FROM   recyclebin;
   
   RECYCLE_NAME                      ORIGINAL_NAME          TYPE
   --------------------------------  ---------------------  ----------
   BIN$gk3lsj/3akk5hg3j2lkl5j3d==$0  EMPLOYEE_DEMO          TABLE
   BIN$JKS983293M1dsab4gsz/I249==$0  I_EMP_DEMO             INDEX
   

   If you plan to manually restore original names for dependent objects, then ensure that you make note of each dependent object's system-generated recycle bin name before you restore the table.

   Note:

   Object views such as DBA_TABLES do not display the recycle bin objects.

3. Optionally, query the table in the recycle bin.

   You must use the recycle bin name of the object in your query rather than the object's original name. The following example queries the table with the recycle bin name of BIN$gk3lsj/3akk5hg3j2lkl5j3d==$0:

   SELECT * 
   FROM  "BIN$gk3lsj/3akk5hg3j2lkl5j3d==$0";
   

   Quotation marks are required because of the special characters in the recycle bin name.

   Note:

   If you have the necessary privileges, then you can also use Flashback Query on tables in the recycle bin, but only by using the recycle bin name rather than the original table name. You cannot use Data Manipulation Language (DML) or DDL statements on objects in the recycle bin.

4. Retrieve the dropped table.

   Use the FLASHBACK TABLE ... TO BEFORE DROP statement. The following example restores the BIN$gk3lsj/3akk5hg3j2lkl5j3d==$0 table, changes its name back to hr.employee_demo, and purges its entry from the recycle bin:

   FLASHBACK TABLE "BIN$gk3lsj/3akk5hg3j2lkl5j3d==$0" TO BEFORE DROP;
   

   The table name is enclosed in quotation marks because of the possibility of special characters appearing in the recycle bin object names.

   Alternatively, you can use the original name of the table:

   FLASHBACK TABLE HR.EMPLOYEE_DEMO TO BEFORE DROP;
   

   You can also assign a new name to the restored table by specifying the RENAME TO clause. For example:

   FLASHBACK TABLE "BIN$gk3lsj/3akk5hg3j2lkl5j3d==$0" TO BEFORE DROP 
     RENAME TO hr.emp_demo;
   

5. Optionally, verify that all dependent objects retained their system-generated recycle bin names.

   The following query determines the names of the indexes of the retrieved hr.employee_demo table:

   SELECT INDEX_NAME 
   FROM   USER_INDEXES 
   WHERE  TABLE_NAME = 'EMPLOYEE_DEMO';
   
   INDEX_NAME
   ------------------------------
   BIN$JKS983293M1dsab4gsz/I249==$0
   

6. Optionally, rename the retrieved indexes to their original names.

   The following statement renames the index to its original name of i_emp_demo:

   ALTER INDEX "BIN$JKS983293M1dsab4gsz/I249==$0" RENAME TO I_EMP_DEMO;
   

7. If the retrieved table had referential constraints before it was placed in the recycle bin, then re-create them.

   This step must be performed manually because the recycle bin does not preserve referential constraints on a table.

To use the FLASHBACK DATABASE command to return your database contents to points in time within the flashback window, your database must have been previously configured for flashback logging as described in "Overview of Flashback Database, Restore Points and Guaranteed Restore Points". To return the database to a guaranteed restore point, you must have previously defined a guaranteed restore point as described in "Using Normal and Guaranteed Restore Points".

Flashback Database works by undoing changes to the data files that exist at the moment that you run the command. Note the following important prerequisites:

• No current data files are lost or damaged. You can only use FLASHBACK DATABASE to rewind changes to a data file made by an Oracle database, not to repair media failures.

• You are not trying to recover from accidental deletion of data files, undo a shrink data file operation, or undo a change to the database name.

• You are not trying to use FLASHBACK DATABASE to return to a point in time before the restore or re-creation of a control file. If the database control file is restored from backup or re-created, then all accumulated flashback log information is discarded.

• You are not trying to use FLASHBACK DATABASE to undo a compatibility change.

1. Ensure that the prerequisites described in Prerequisites of Flashback Database are met.
2. Connect SQL*Plus to the target database and determine the desired SCN, restore point, or point in time for the FLASHBACK DATABASE command.

   Obtain the earliest SCN in the flashback database window as follows:

   SELECT OLDEST_FLASHBACK_SCN, OLDEST_FLASHBACK_TIME
   FROM   V$FLASHBACK_DATABASE_LOG;
   

   The most recent SCN that can be reached with Flashback Database is the current SCN of the database. The following query returns the current SCN:

   SELECT CURRENT_SCN
   FROM   V$DATABASE;
   

   You can query available guaranteed restore points as follows (sample output included):

   SELECT NAME, SCN, TIME, DATABASE_INCARNATION#,
          GUARANTEE_FLASHBACK_DATABASE
   FROM   V$RESTORE_POINT
   WHERE  GUARANTEE_FLASHBACK_DATABASE='YES';
    
   NAME                   SCN TIME                  DATABASE_INCARNATION# GUA
   --------------- ---------- --------------------- --------------------- ---
   BEFORE_CHANGES     5753126 04-MAR-12 12.39.45 AM                     2 YES
   

   Note:

   If the flashback window does not extend far enough back into the past to reach the desired target time, and if you do not have a guaranteed restore point at the desired time, then you can achieve similar results by using database point-in-time recovery, as described in "Performing Database Point-in-Time Recovery".

3. Shut down the database consistently, ensure that it is not opened by any instance, and then mount it:

   SHUTDOWN IMMEDIATE;
   STARTUP MOUNT;
   

4. Repeat the query in Step 2 of this procedure.

   Some flashback logging data is generated when the database is shut down. If flashback logs were deleted due to space pressure in the fast recovery area, then your target SCN may not be reachable.

   Note:

   If you run FLASHBACK DATABASE when your target SCN is outside the flashback window, then FLASHBACK DATABASE fails with an ORA-38729 error. In this case your database does not change.

5. Start RMAN and connect to the target database.

   See Also:

   "Making Database Connections with RMAN"

6. Run the SHOW command to see which channels are preconfigured.

   During the flashback operation, RMAN may need to restore archived redo logs from backup. Enter the following command to see whether channels are configured (sample output is included):

   SHOW ALL;
   
   RMAN configuration parameters for database with db_unique_name PROD1 are:
   .
   .
   .
   CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default
   CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # default
   CONFIGURE DEVICE TYPE SBT_TAPE PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # default
   CONFIGURE CHANNEL DEVICE TYPE 'SBT_TAPE' PARMS  "SBT_LIBRARY=/usr/local/oracle/backup/lib/libobk.so";
   

   If the necessary devices and channels are configured, then no action is necessary. Otherwise, use the CONFIGURE command to configure automatic channels, or include ALLOCATE CHANNEL commands within a RUN block.

7. Run the RMAN FLASHBACK DATABASE command.

   You can specify the target time by using a form of the command shown in the following examples:

   FLASHBACK DATABASE TO SCN 46963;
   
   FLASHBACK DATABASE 
     TO RESTORE POINT BEFORE_CHANGES;
   
   FLASHBACK DATABASE TO TIME   
     "TO_DATE('09/20/12','MM/DD/YY')";
   

   When the FLASHBACK DATABASE command completes, the database is left mounted and recovered to the specified target time.

8. Open the database read-only in SQL*Plus and run some queries to verify the database contents.

   Open the database read-only as follows:

   ALTER DATABASE OPEN READ ONLY;
   

   If you are satisfied with the state of the database, then end the procedure with Step 9. If you are not satisfied with the state of the database, skip to Step 10.

9. If you are satisfied with the results, then perform either of the following mutually exclusive actions:

   • Make the database available for updates by opening the database with the RESETLOGS option. If the database is currently open read-only, then execute the following commands in SQL*Plus:

     SHUTDOWN IMMEDIATE
     STARTUP MOUNT
     ALTER DATABASE OPEN RESETLOGS;
     

     Note:

     After you perform this OPEN RESETLOGS operation, all changes to the database after the target SCN for FLASHBACK DATABASE are abandoned. Nevertheless, you can use the technique in "Rewinding the Database to an SCN in an Abandoned Incarnation Branch" to return the database to that range of SCNs while they remain in the flashback window.

   • Use Oracle Data Pump Export to make a logical backup of the objects whose state was corrupted. Afterward, use RMAN to recover the database to the present time:

     RECOVER DATABASE;
     

     This step undoes the effect of the Flashback Database by reapplying all changes in the redo logs to the database, returning it to the most recent SCN.

     After reopening the database read/write, you can import the exported objects with the Data Pump Import utility. See Oracle Database Utilities to learn how to use Data Pump.

10. If you find that you used the wrong restore point, time, or SCN for the flashback, then mount the database and perform one of the following mutually exclusive options:

    • If your chosen target time was not far enough in the past, then use another FLASHBACK DATABASE command to rewind the database further back in time:

      FLASHBACK DATABASE TO SCN 42963;  #earlier than current SCN 
      

    • If you chose a target SCN that is too far in the past, then use RECOVER DATABASE UNTIL to wind the database forward in time to the desired SCN:

      RECOVER DATABASE UNTIL SCN 56963; #later than current SCN 
      

    • If you want to completely undo the effect of the FLASHBACK DATABASE command, then you can perform complete recovery of the database by using the RECOVER DATABASE command without an UNTIL clause or SET UNTIL command:

      RECOVER DATABASE;
      

      The RECOVER DATABASE command reapplies all changes to the database, returning it to the most recent SCN.

1. Start RMAN and connect to the root as a user with the SYSBACKUP or SYSDBA privilege.

   See Also:

   "Making RMAN Connections to a CDB"

2. Determine the target time to which the CDB must be recovered.
3. Take all files that correspond to the PDB for which PITR was performed offline.

   Use the ALTER PLUGGABLE DATABASE command to take the files offline

4. Rewind the CDB to the desired target time. This operation does not affect the PDB whose files are offline.

   Use the FLASHBACK DATABASE command to rewind the CDB.

5. Recover the PDB for which PITR was performed.

   Use the RESTORE PLUGGABLE DATABASE and RECOVER PLUGGABLE DATABASE commands.

The prerequisites for database point-in-time recovery (DBPITR) are as follows:

• Your database must be running in ARCHIVELOG mode.

• You must have backups of all data files from before the target SCN for DBPITR and archived logs for the period between the SCN of the backups and the target SCN.

• If the backups were encrypted using transparent encryption, and if a password-based software keystore was used, then the keystore password must be provided before the restore operation is performed. Use the SET command with the DECRYPTION WALLET OPEN IDENTIFIED BY option to specify the password that must be used to open the password-based keystore. Note that this command is not required when an auto-login software keystore is used.

  See Also:

  Oracle Database Backup and Recovery Reference for the syntax and usage of the SET command

For a complete account of command prerequisites and usage notes, refer to the RECOVER entry in Oracle Database Backup and Recovery Reference.

RMAN enables you to perform point-in-time recovery (PITR) of CDBs and PDBs. PITR for PDBs can only be performed using RMAN. If you are not using a recovery catalog, it is recommended that you turn on control file auto backups. Otherwise, PITR for PDBs may not work effectively when RMAN needs to undo data file additions or deletions.

The information in this chapter about PITR applies to CDBs, with the differences described in the following sections.

When you perform DBPITR of a PDB, all the data files for this PDB are recovered in-place. However, to recover the PDB to the specified target time, RMAN also needs the UNDO tablespace as it existed at the target time. Because the UNDO tablespace is shared by all PDBs, it cannot be recovered in-place. RMAN restores the UNDO, SYSTEM, and SYSAUX tablespaces in the root to an auxiliary database and then uses the undo information to recover the PDB to the target time.If a fast recovery is configured, Oracle Database uses it as the auxiliary destination. If the fast recovery area is not configured, then you must use the AUXILIARY DESTINATION clause to specify the location used for auxiliary database files. Ensure that there is sufficient space in the fast recovery area to restore the root tablespaces and the undo tablespace. If the fast recovery area does not have the required space, use an alternate location by specifying the AUXILIARY DESTINATION clause.

1. Connect SQL*Plus to the target database and verify that the beginning of the flashback window is earlier than the time of the most recent OPEN RESETLOGS.

   Run the following queries:

   SELECT RESETLOGS_CHANGE# 
   FROM   V$DATABASE;
   
   SELECT OLDEST_FLASHBACK_SCN 
   FROM   V$FLASHBACK_DATABASE_LOG;
   

   If V$DATABASE.RESETLOGS_CHANGE# is greater than V$FLASHBACK_DATABASE_LOG.OLDEST_FLASHBACK_SCN, then you can use Flashback Database to reverse the OPEN RESETLOGS. operation

2. Shut down the database, mount it, and recheck the flashback window. If the resetlogs SCN is still within the flashback window, then proceed to the next step.
3. Connect RMAN to the target database.

   See Also:

   "Making Database Connections with RMAN"

4. Perform a flashback to the SCN immediately before the RESETLOGS.

   Use the following form of the FLASHBACK DATABASE command:

   FLASHBACK DATABASE TO BEFORE RESETLOGS;
   

   As with other uses of FLASHBACK DATABASE, if the target SCN is before the beginning of the flashback database window, an error is returned and the database is not modified. If the command completes successfully, then the database is left mounted and recovered to the most recent SCN before the OPEN RESETLOGS operation in the previous incarnation.

5. Open the database read-only in SQL*Plus and perform queries as needed to ensure that the effects of the logical corruption have been reversed.

   Open the database read-only as follows:

   ALTER DATABASE OPEN READ ONLY;
   

6. To make the database available for updates again, shut down the database, mount it, and then execute the following command:

   ALTER DATABASE OPEN RESETLOGS;
   

1. Use SQL*Plus to connect to the target database and verify that the flashback logs contain enough information to flash back to the SCN.

   For example, execute the following query:

   SELECT OLDEST_FLASHBACK_SCN
   FROM   V$FLASHBACK_DATABASE_LOG;
   

2. Determine the target incarnation number for the Flashback Database operation, that is, the incarnation key for the parent incarnation.

   For example, execute the following query:

   SELECT PRIOR_INCARNATION# 
   FROM   V$DATABASE_INCARNATION 
   WHERE  STATUS = 'CURRENT';
   

3. Start RMAN and connect to the target database.

   See Also:

   "Making Database Connections with RMAN"

4. Shut down the database, and then mount it as follows:

   SHUTDOWN IMMEDIATE;
   STARTUP MOUNT;
   

5. Set the database incarnation to the parent incarnation.

   For example, use the following command to return to incarnation 1:

   RESET DATABASE TO INCARNATION 1;
   

6. Run the FLASHBACK DATABASE command, specifying the target SCN.

   For example, use the following command to rewind the database to SCN 1500:

   FLASHBACK DATABASE TO SCN 1500;
   

7. Open the database read-only in SQL*Plus and perform queries as needed to ensure that the effects of the logical corruption have been reversed.

   Open the database read-only as follows:

   ALTER DATABASE OPEN READ ONLY;
   

8. To make the database available for updates again, shut down the database, mount it, and then execute the following command:

   ALTER DATABASE OPEN RESETLOGS;
   

1. Start RMAN and connect to a target database and recovery catalog.

   See Also:

   "Making Database Connections with RMAN"

2. Determine which database incarnation was current at the time of the backup.

   Use LIST INCARNATION to find the primary key of the incarnation that was current at the target time:

   LIST INCARNATION OF DATABASE trgt;
   
   List of Database Incarnations
   DB Key  Inc Key   DB Name   DB ID       STATUS     Reset SCN    Reset Time
   ------- -------   -------   ------      -------    ----------   ----------
   1       2         TRGT      1224038686  PARENT     1            02-OCT-13
   1       582       TRGT      1224038686  CURRENT    59727        10-OCT-13
   

   Look at the Reset SCN and Reset Time columns to identify the correct incarnation, and note the incarnation key in the Inc Key column. In this example, the backup was made 2 October 2013. In this case, the incarnation key value is 2.

3. Ensure that the database is started but not mounted.

   STARTUP FORCE NOMOUNT;
   

4. Reset the target database to the incarnation obtained in Step 2.

   In this example, specify the incarnation current at the time of the backup of 2 October. Use the value from the Inc Key column to identify the incarnation.

   RESET DATABASE TO INCARNATION 2;
   

5. Restore and recover the database, performing the following actions in the RUN command:

   • Set the end time for recovery to the time just before the loss of the data.

   • Allocate any channels required that are not configured.

   • Restore the control file from the October 2 backup and mount it.

   • Restore the data files and recover the database. Use the RECOVER DATABASE ... UNTIL command to perform DBPITR, bringing the database to the target time of 7:55 a.m. on October 8, just before the data was lost.

   The following example shows all of the steps required in this case:

   RUN
   {
     SET UNTIL TIME 'Oct 8 2013 07:55:00'; 
     RESTORE CONTROLFILE;
     # without recovery catalog, use RESTORE CONTROLFILE FROM AUTOBACKUP
     ALTER DATABASE MOUNT; 
     RESTORE DATABASE;
     RECOVER DATABASE;
   }
   ALTER DATABASE OPEN RESETLOGS;
   

   See Also:

   Oracle Database Backup and Recovery Reference for details about the RESET DATABASE command