Oracle RAC Backup and Recovery - Learnomate Technologies

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25 Jul, 2025
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Oracle RAC Backup and Recovery

1 . RAC Backup and Recovery Concepts

Backup in RAC: In Oracle RAC, backups are crucial for ensuring data integrity and availability. RAC backups are performed across multiple instances of the cluster, and RMAN (Recovery Manager) coordinates backup activities.

Parallelism: RAC allows parallel backups using RMAN, utilizing multiple nodes and channels, which speeds up the process.

Backup Types: Includes full backups, incremental backups, and archivelog backups. These can be performed at the database, tablespace, or datafile level.

Recovery Concepts: RAC recovery involves restoring data and bringing it to a consistent state across all instances. Common scenarios include instance recovery, media recovery, and complete or point-in-time recovery.

2 . Configuring RMAN for RAC

RMAN Configuration: RMAN must be configured to handle multiple instances in a RAC environment. The configuration is stored in the database control file or recovery catalog.

Channel Configuration: RMAN uses channels for backup and recovery operations. In RAC, you can configure multiple channels to distribute the load across instances.

Automatic Channel Allocation: RMAN automatically allocates channels across RAC nodes based on the load, but this can also be manually configured.

Instance-Specific Backups: You can perform instance-specific backups, though typically backups are coordinated across all instances.

3 . Performing RAC Backups Using RMAN

Full Database Backup: A full backup can be taken across all RAC instances simultaneously, ensuring consistency.

Incremental Backup: Incremental backups capture only the changes since the last backup, reducing the backup size and duration. RMAN manages incremental backups efficiently across all RAC nodes.

Archivelog Backup: Archive logs generated on all RAC nodes need to be backed up to ensure that all committed transactions can be recovered.

Backup Storage: Backups can be stored on ASM disk groups, file systems, or external storage. RAC environments often use shared storage to centralize backups.

4 . RAC Recovery Scenarios

Instance Recovery: If a RAC node fails, the surviving instances perform instance recovery, automatically applying the redo logs to ensure data consistency.

Media Recovery: If data files are lost or corrupted, you can restore them from backups and perform recovery using the archived redo logs and RMAN.

Disaster Recovery: In severe cases where multiple nodes or the entire cluster is affected, complete recovery using backups and archived logs is necessary. RMAN can automate this process across nodes.

Point-in-Time Recovery: In cases of logical corruption, point-in-time recovery (PITR) can be used to restore the database to a previous state. This can be done for the entire database or specific tablespaces.

5 . Flashback Technology in RAC Environments

Flashback Overview: Flashback technology in Oracle RAC provides a set of features that allow you to quickly undo changes to the database without needing a full restore from backups.

Flashback Database: Enables you to rewind the entire RAC database to a previous point in time, useful for recovering from logical errors like accidental data deletion.

Flashback Table: Allows you to revert specific tables to a previous state without affecting the rest of the database.

Flashback Drop: Provides the ability to recover dropped tables from the recycle bin.
Flashback Data Archive: Maintains historical versions of data, allowing you to query older versions of rows.

6 . What are the high level steps to convert a non-RAC database to RAC database?

Two phase approach can be followed to convert a database from non-RAC to RAC.

Duplicate single instance non-ASM database to ASM using RMAN
Manually convert single instance database to RAC

Prerequisites

Install and configure Clusterware

Install and configure Automatic Storage Management (ASM)

Install Oracle Database Software

Standalone database and RAC must be on same Database version

Estimate used space for Non-RAC database
Create password file and init.ora file for RAC environment

Initfile contents (basic)

db_name ="ORADB"  

instance_name =ORADB  

control_files =‘+DATA’, ‘+FLASH’  

db_create_file_dest='+DATA'  

db_recovery_file_dest='+FLASH'  

db_create_online_dest_1=’+DATA’  

db_create_online_dest_2=’+FLASH’  

log_archive_dest_1='LOCATION=+FLASH’

Configure Oracle Listener and tnsnames.ora file
Duplicate the database to RAC server using RMAN