Oracle RAC Backup and Recovery

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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. 

1. Duplicate single instance non-ASM database to ASM using RMAN 
2. 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  

1. Estimate used space for Non-RAC database 
2. 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’  

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