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