RMAN Backups Methodology Full and Incremental

RMAN provides multiple backup types, but the most commonly used in production environments are Full backups and Incremental backups. Understanding their differences helps DBAs design efficient backup strategies that optimize storage, speed, and recovery time.

1. Full Backup

A Full Backup (or Level 0 backup) is a complete backup of the entire database.

Key Characteristics

Backs up all data blocks, regardless of whether they changed.

Forms the baseline for incremental backup strategies.

Larger in size than incremental backups.

Takes more time and requires more storage.

Recovery is straightforward—restore full backup + apply archived logs.

2. Incremental Backups

Incremental backups only capture blocks that have changed since a previous L0 backup.

RMAN supports two types:

Differential Incremental Backup (Level 1 Differential)

Cumulative Incremental Backup (Level 1 Cumulative)

Both rely on a Level L0 full backup as a baseline.

2.1. Differential Incremental Backup

A Differential Level 1 backup captures all blocks changed since the last backup (Level 0 or Level 1).

Key Characteristics

Smaller and faster than full backups.

Captures daily changes.

During recovery, RMAN may use multiple Level 1 backups.

When it comes to recovery we need L0 Backup and all L1 backups including Archive logs need to be apply.

2.2. Cumulative Incremental Backup

A Cumulative Level 1 backup captures all blocks changed since the last Level 0.

Key Characteristics

Slightly larger than differential backups.

Faster recovery (fewer incremental files to apply).

Preferred for large, mission-critical systems.

When it comes to recovery we need L0 and recent L1 Cumulative backup including Archive logs need to be apply.

Understanding RMAN ( Recovery Manager) and Backups

 RMAN Key Points:

    - RMAN (Recovery Manager)

    - Oracle Database backup and recovery automation

    - It Introduced in Oracle 8i version

    - It performs block level backup

    - Parallelism

    - Detecting corruption in datafiles

    - Validating the backup

    - Incremental Backup

    - Recovery Catalog etc

    - Multi Destination Backups

    - Archive log mode is must to use RMAN

RMAN is faster because it takes block level backups.

RMAN is faster because we can initiate parallel processes.

RMAN will data block corruptions and repair it for you.

RMAN stores backup metadata information in the database control file, you can also store the information into deferent database on different server which is called as RECOVERY catalog

RMAN Incremental Recovery

              - Level 0 - Full database backup

              - Level 1 - Backup of only changed blocks taken by referring data block header for updated SCN

              -  

              - As per recovery, we must only restore the database from level 0 and recovery the Database using level 1. When you try to take level 1 backup, RMAN checks if already you have level 0 backup or not. If not then it will take level 0 backup automatically.

Recovery is of two parts:

              - Restore and Recover - We cannot perform recovery without restore. Hence Level 0 is used for restore and level 1 is used for recovery.

RMAN configuration Items

              - show all;

RMAN Utility:

RMAN utility comes with Oracle Binaries

No special installation or license required for using RMAN

At command prompt just type rman

It defaults connects to database environmental variables defined

RMAN utility can be used only when your DB is in at least MOUNT stage

RMAN is used while the DB is up and running and have very little performance impact if the backup is running

RMAN Backup Methodology:

- Full Backup

        - Entire Database backup plus archive logs 

        - Cannot apply Incremental backup on full backup

                            

- Incremental Backup

        - Level 0 - FULL Database backup

        - Level 1 - Backup changes only from last incremental backup

- Differential Backup 

                - Cumulative Backup

Components of RMAN:

  - RMAN Prompt

  - Target Database

  - Recovery Catalog

  - Auxiliary Database --- When cloning, Clone DB is called as auxiliary Database

  - Media Management Layer --- layer between RMAN 3rd part vendor backup tools netbackup,  Veritos and Tape backups

  - RMAN Channels

RMAN Configuration Parameter:

- RETENTION POLICY - tells till what date our backup will be stored which we can use for recovery

               - Redundancy -- How many backups to be retained

               - Recover Window -- How many days backup to be retained

        - Channels -- You can define channel to take backup to disk or tape

        - Control file auto backup -- includes control file and spfile auto backup

        - Parallelism -- Creates multiple processes to speed up backup

        - Encryption -- to secure the backup

Backups and RMAN Backups ( Recovery Manager)

 

Why we need backup

The primary purpose of taking backups is to protect the database from data loss and ensure the ability to reconstruct the database in case of corruption, errors, or failures.

Categories of Database Failure:

Data loss can occur at any time

       Human errors, accidental deletions, logical corruption, hardware failures, or storage issues can lead to partial or complete data loss.

Backups preserve data integrity

    When data corruption or inconsistencies arise, backups enable you to restore the database to a consistent and trustworthy state.

Support for disaster recovery

    In the event of serious failures—like server crashes, media corruption, or site outages—backups are the foundation for bringing the database back online.

Compliance and business continuity

    Many industries require proper backup policies to meet audit standards and ensure uninterrupted business operations.

Backup Types:

Oracle backups are broadly classified into two categories:

1. Logical Backups

Logical backups extract database objects in a logical format.

Examples: Table-level, Schema-level and Tablespace-level export

Tools Used: Data Pump (expdp / impdp) and  Export/Import (exp / imp)

Logical backups are mainly used for:

    Application-level migrations

    Object-level recoveries

    Copying data between databases

2. Physical Backups

Physical backups involve copying actual database files at the OS level.

Files Included Datafiles, Control files, SPFILE and Archived redo logs

Types of Physical Backups

    RMAN Backups (most recommended)

    Hot Backup (User‑Managed Online Backup)

    Cold Backup (User‑Managed Offline Backup)

Hot and Cold Backups

Hot and Cold backups are known as manual backups, as they are performed manually without using RMAN or any backup tool.

Cold Backup (Consistent Backup)

    Database is shut down.

    All database files are copied at OS level.

    Backup is consistent.

    No recovery required during restore.

    Also referred to as a consistent backup.

Hot Backup (Inconsistent Backup)

    Database is open and available to users.

    Tablespaces are placed in backup mode.

    Datafiles are copied manually at OS level.

    Recovery is required because the backup is inconsistent.

    Archived logs are needed for full recovery.

Backup States / Backup Types in Oracle

Oracle backups fall under two main categories based on the state of the database:

1) Consistent Backup

    A backup is consistent when: The database is shut down cleanly using SHUTDOWN IMMEDIATE / NORMAL / TRANSACTIONAL.

All files (datafiles, control files, redo logs) are synchronized.

2) Inconsistent Backup

A backup is inconsistent when the database is in OPEN or MOUNT mode during the backup.

Files are not synchronized; hence recovery is mandatory.

Examples

    Hot Backup (User‑managed online backup)

    RMAN Backups (always inconsistent unless database is closed)

Oracle RMAN (Recovery Manager)

Oracle Recovery Manager (RMAN) is a powerful, built‑in Oracle database utility used for performing backup, restore, and recovery operations. It is a no‑cost, command‑line tool provided by Oracle to help DBAs protect critical database files—including datafiles, control files, SPFILEs, and archived redo logs.

RMAN integrates tightly with the Oracle database engine, enabling advanced features such as:

Block‑level corruption detection

RMAN scans blocks during backup and restore operations, identifying corrupted blocks early and ensuring data integrity.

Automated backup retention policies

You can define retention periods or redundancy levels, and RMAN will automatically manage obsolete backups.

Backup compression

Built‑in compression reduces storage costs and speeds up backup operations.

Parallelization

File identification

Block recovery

Media recovery

RMAN can run backup and restore operations across multiple channels, improving performance and meeting high‑availability needs.

What to Backup 

Parameter file / SPfile , Control file , archive log files and data files

What file needed in different stages of database 

1) Shutdown - Nothing needed

2) No Mount - Pfile or SPfile

3) Mount - Control file

4) Open - Data and redo log files

Recovery:

       1. Complete Recovery

          --- Recovering the database exactly till the point of failure

                                          

       2. Incomplete Recovery

          --- It cannot recover the database till the point of failure

  --- You can recover the database till the time you had taken the backup