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NetVault Plug-in for Oracle 13.0 - User Guide

Introducing Quest® NetVault® Plug-in  for Oracle Defining a backup strategy Installing and removing the plug-in Configuring the plug-in Backing up data Using the Oracle Flashback Database Restoring data
Restoring and recovering data: an overview Performing User Managed restores Using advanced User Managed restore procedures Performing RMAN restores Using RMAN types of recovery in a non-RAC environment Using advanced procedures with RMAN restores
Maintaining the Recovery Catalog Using the RMAN CLI Using the plug-in with Oracle RAC Using the plug-in in a failover cluster environment Using the plug-in with Oracle Data Guard Using the plug-in with Oracle Container Databases (CDBs) and Pluggable Databases (PDBs) Troubleshooting

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, and SQL queries. 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.
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 the job
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Recovering the database
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Opening the database for use

Preparing the database for recovery

You do not have to take a complete Oracle database offline to restore selected tablespaces, but you must take each tablespace that you want to restore offline before performing the restore.

1
Connect to the database with SYSDBA privileges by using the SQL*Plus utility.
SQLPLUS SYS AS SYSDBA
2
If the database is open, take all tablespaces that contain damaged datafiles offline by running the following command:
ALTER TABLESPACE <Tablespace Name> OFFLINE IMMEDIATE;

Selecting data for a restore

1
In the Navigation pane, click Create Restore Job.
2
To filter the items displayed in the saveset table, click Filter .
The table displays the saveset name (job title and saveset ID), creation date and time, size, and catalog status. By default, the list is sorted alphabetically by creation date.
3
In the saveset table, select the applicable saveset.
When you select a saveset, the following details are displayed in the Saveset Information area: Job ID, job title, server name, client name, plug-in name, saveset date and time, retirement setting, Incremental Backup or not, Archive or not, and saveset size.
4
Select one of the following options:
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Restore All Using Defaults: To restore using the prepopulated defaults, click this button, and proceed to Finalizing and submitting the job.
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Restore: To use the Create Selection Set page to select the items that you want to restore, click this button and proceed to the next step.
5
On the Create Selection Set page, select the data that you want to restore.
Depending on the items selected for the backup, the saveset includes:
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Parameter File
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All Tablespaces
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Backup Control File
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Archive Logs
6
Open the applicable items, and select the data that you want to include in the restore.
 
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NOTE: For User Managed restores, you do not have to set any other options; the Restore Options tab does not contain any fields.
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