🛠️ Understanding Obsolete Backups in Oracle RMAN

In Oracle RMAN (Recovery Manager), managing obsolete backups is crucial for storage optimization and database performance. In this post, we'll explore:

✅ What are obsolete backups?
✅ The difference between recovery window and redundancy.
✅ How to identify and delete obsolete backups efficiently.

📌 What Are Obsolete Backups in RMAN?

An obsolete backup is any backup older than the defined retention policy. These backups are no longer needed for recovery and can be deleted to free up space.

🔍 How Are Backups Marked as Obsolete?

RMAN classifies backups as obsolete based on:
1️⃣ Recovery Window Policy (Time-Based)
2️⃣ Redundancy Policy (Count-Based)

Let’s break them down:

⏳ Recovery Window in RMAN

A recovery window specifies how many days of backups should be retained. Any backups older than this window are marked as obsolete.

📌 Example:
If the recovery window is set to 7 days, RMAN keeps backups for the last 7 days. Any backups older than 7 days are obsolete and can be deleted.

🔎 How to Check the Recovery Window?
Run this command in RMAN:

SHOW ALL;

This will display the retention policy, including the recovery window settings.

🔁 Redundancy in RMAN

Redundancy defines the number of backup copies RMAN should keep. When new backups are taken, old backups beyond the redundancy limit become obsolete.

📌 Example (Redundancy = 2):

  • Backup 1, Backup 2 (Kept)
  • Backup 3 (Oldest backup now obsolete)
  • Backup 4 (Backup 2 becomes obsolete)
  • Backup 5 (Backup 3 becomes obsolete)

This method ensures that only the latest backups are retained, regardless of how old they are.

📊 How to Find and Delete Obsolete Backups?

🔍 Checking Obsolete Backups

To identify obsolete backups, use:

REPORT OBSOLETE;

This command analyzes RMAN's retention policy and lists backups that are no longer required.

🗑️ Deleting Obsolete Backups

To remove obsolete backups automatically, run:

DELETE OBSOLETE;

⚠️ Warning: This command permanently deletes obsolete backups, so verify the report before executing.

How to change the recovery window?

configure retention policy to recovery window of 2 days;

Recovery window changed 2 days.




💡 Key Takeaways

✅ Obsolete backups are those older than the recovery window or exceeding redundancy limits.
✅ Recovery Window Policy keeps backups for a specific number of days.
✅ Redundancy Policy keeps only a set number of backups, regardless of age.
✅ Use REPORT OBSOLETE to check obsolete backups.
✅ Use DELETE OBSOLETE to remove them and free up storage space.

By regularly managing obsolete backups, you can optimize disk space, improve backup performance, and ensure a reliable Oracle database recovery strategy. 🚀

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