RMAN (Recovery Manager) and traditional user-managed backup and recovery methods have significant differences in their approach, control, and flexibility. The main differences between these two methods are explained below.
1. Control and Automation: User-managed backup and recovery involve manual processes, and the DBA must execute each step manually. On the other hand, RMAN is a highly automated backup and recovery tool that provides centralized control over backup and recovery operations. It automates entire backup and recovery operations and eliminates the need for manual intervention.
2. Backup and Recovery Optimization: RMAN provides several optimization techniques like backup multiplexing, backup set compression, and dual tape streams that cannot be achieved in user-managed backups. These optimizations significantly reduce backup time and the volume of backup data to be stored, which results in faster restore times.
3. Incremental Backups and Recovery: Another significant difference between RMAN and User-managed backups is the concept of incremental backups. With User-managed backups, DBA can only perform full backups, while with RMAN, incremental backups can be taken, reducing the backup size and time. While restoring the database, RMAN can stitch together different backups to recover the database to any point in time with minimal data loss.
4. Backup Validation: RMAN can perform a checksum check on the backup pieces, validating the backup after completion. In comparison, user-managed backup needs manual validation for the backups, increasing the possibility of data corruption or inconsistency in backup format.
5. Data Corruption Detection and Recovery: With user-managed backups, restoring a corrupt backup requires detective work and trial and error based on timestamps to identify where data is corrupt. RMAN has in-built functionality to detect data block corruption, and it can recover data from the remaining blocks.
6. Backup Encryption: RMAN can encrypt backup data during transit and storage. In comparison, user-managed backups require third-party tools to encrypt backups, adding complexity and maintenance costs.
In conclusion, RMAN offers efficient, controlled, and optimized backup and recovery operations. It offers advanced functionality, which makes it the preferred choice for Oracle database backup and recovery. Also, using RMAN enables DBA to ensure database recoverability and meet the RTO/RPO (recovery point objective / recovery time objective) targets.