NetVault Plug-in for Oracle 7.1

System Change Number (SCN) Based Point-in-Time Recovery – When an SCN is specified during PIT Recovery, RMAN will recover up to, but not including, the specified SCN. For example, if SCN 1000 is specified, recovery up to SCN 999 is performed.

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Log Sequence Number (LSN) Based Point-in-Time Recovery – When the exact time of the data corruption or failure is not known, specifying a Log Sequence Number that contains the target SCN is a viable option. RMAN will recover through the specified log. V$LOG_HISTORY can be queried to view the logs that have been archived to identify the appropriate log sequence number and thread.

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Time Based Point-in-Time Recovery – Time-based PIT Recovery is useful when the time that the data corruption occurred is known. For example, if a developer dropped a table at 6:00 a.m., PIT Recovery can be performed with a stop time of 5:55 a.m. The plug-in will recover up to, but not including, the specified time.

For more information on PIT Recovery and database incarnations, refer to Performing Database Point-in-Time Recovery in the Oracle Database Backup and Recovery Basics guide.

Block Media Recovery

Block Media Recovery is only available in the Oracle Enterprise Edition. This feature reduces downtime by letting you recover only the blocks that were corrupted instead of restoring and recovering the entire datafile. Block Media Recovery is most useful for physical corruption problems that involve a small, well-known number of blocks. Block-level data loss usually results from intermittent, random I/O errors that do not cause widespread data loss, and memory corruptions that get written to disk. Block Media Recovery is not intended for cases where the extent of data loss or corruption is unknown and the entire datafile requires recovery. In such cases, Datafile Media Recovery is the best solution.

You can use Block Media Recovery to recover one or more corrupt data blocks within a datafile. Block Media Recovery provides the following advantages over Datafile Media Recovery:

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It lowers the MTTR because only blocks needing recovery are restored and recovered.

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It lets the affected datafiles remain online during recovery.

Without Block Media Recovery, if even a single block is corrupt, you must take the datafile offline and restore the datafile from a backup. You must apply all redo logs generated for the datafile after the backup was created. The entire file is unavailable until media recovery completes. With Block Media Recovery, only the blocks actually being recovered are unavailable during the recovery.

Prerequisites

In addition to running the Oracle Enterprise Edition, Oracle requires the following prerequisites for Block Media Recovery to be met as defined in Performing Block Media Recovery of the Oracle Database Backup and Recovery User’s Guide.

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The target database must run in ARCHIVELOG mode and be open or mounted with a current Control File.

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The target database must not be a standby database.

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The backups of the datafiles containing the corrupt blocks must be Full or Incremental Level 0 backups and not proxy copies.

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RMAN can use only archived redo logs for the recovery. RMAN cannot use Incremental Level 1 Incremental Backups. Block Media Recovery cannot survive a missing or inaccessible archived redo log, although it can sometimes survive missing redo records.

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Flashback Database must be enabled on the target database for RMAN to search the flashback logs for good copies of corrupt blocks. When flashback logging is enabled and contains older, uncorrupted versions of the corrupt blocks, RMAN can use these blocks, possibly speeding up the recovery.

Identifying corrupted blocks

The V$DATABASE_BLOCK_CORRUPTION view displays blocks marked corrupt by database components such as RMAN commands, ANALYZE, SQL queries, and so on. Physical corruption, sometimes called media corruption, results in rows being added to this view. For example, the database does not recognize the block: the checksum is invalid, the block contains all zeros, or the block header is fractured.

In addition to being reported in V$DATABASE_BLOCK_CORRUPTION, block corruption is also reported in the following locations:

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Results of the LIST FAILURE, VALIDATE, or BACKUP … VALIDATE command

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Error messages in standard output

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Oracle Alert Log

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User trace files

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Results of the SQL commands ANALYZE TABLE and ANALYZE INDEX

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Results of the DBVERIFY utility

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Third-party media management output such as NetVault Backup.

For example, you may discover the following messages in a user trace file:

ORA-01578: ORACLE data block corrupted (file # 7, block # 3)

ORA-01110: data file 7: '/oracle/oradata/trgt/tools01.dbf'

ORA-01578: ORACLE data block corrupted (file # 2, block # 235)

ORA-01110: data file 2: '/oracle/oradata/trgt/undotbs01.dbf'

Performing User Managed restores

A standard User Managed restore with Plug‑in for Oracle includes the following steps:

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Preparing the database for recovery

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Selecting data for a restore

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Finalizing and submitting a job

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Recovering the database

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Opening the database for use

Preparing the database for recovery

While you do not have to take a complete Oracle Database offline to restore selected tablespaces, each individual tablespace that is to be restored must be taken offline prior to performing the restore.

Connect to the database with SYSDBA privileges via the SQL*Plus utility.

SQLPLUS SYS AS SYSDBA

If the database is open, take all tablespaces that contain damaged datafiles offline by executing the following command:

ALTER TABLESPACE <Tablespace Name> OFFLINE IMMEDIATE;

Selecting data for a restore

To select data to restore

In the Navigation pane, click Create Restore Job.

On the Create Restore Job - Choose Saveset page, select Plug‑in for Oracle from the Plugin Type list.

To filter the items displayed in the saveset table further, use the Client, Date, and Job ID lists.

The table displays the saveset name (Job Title and Saveset ID), creation date and time, and size. By default, the list is sorted alphabetically by saveset name.

In the saveset table, select the applicable item.

When you select a saveset, the following details are displayed in the Saveset Information area: Job ID, Job Title, name of the NetVault Backup Server, name of the client from which the data was backed up, plug-in used to create the saveset, saveset creation date and time, saveset retirement setting, whether it is an Incremental Backup, whether it is an Archive, and saveset size.

To continue, click Next.

On the Create Selection Set page, select the data that you want to restore.

Depending on the items selected for the backup, the saveset will include:

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Open the applicable items, and select the data that you want to include in the restore.