Backup, Recovery, and Disaster Management

This triad forms the core strategy for protecting organizational data from loss or corruption and ensuring business continuity in the event of a failure.

Backup:

A backup is a copy of data that can be used to restore and recover that data. It is a snapshot of the database at a specific point in time.

Types of Backup:

• • Full Backup: A complete copy of the entire database.

  • Differential Backup: Copies only the data that has changed since the last full backup.

  • Incremental Backup: Copies only the data that has changed since the last backup of any type (more efficient but more complex to restore).

• Cold vs. Hot Backup:

  • Cold Backup: Taken when the database is shut down. Ensures a consistent copy but causes downtime.

  • Hot Backup: Taken while the database is online and active. Requires the DBMS to be in a special archiving mode to maintain consistency.

Recovery:

Recovery is the process of restoring the database to a correct, consistent state after a failure, using the backups and logs.

Types of Failures:

• • Transaction Failure: Due to logical errors (e.g., deadlock) or internal conditions (e.g., integer overflow).

  • System Failure: Due to hardware or software faults (e.g., power outage, operating system crash).

  • Media Failure: Due to disk head crash or other storage device destruction.

Recovery Techniques:

• • Deferred Update (No-undo/redo): Transactions do not modify the database until they commit.

  • Immediate Update (Undo/redo): Transactions can modify the database before they commit, requiring both undo and redo actions.

  • Shadow Paging: Maintains two page tables during a transaction; the shadow page table is swapped in at commit.

Disaster Management (Disaster Recovery)

Disaster Management is a broader policy that encompasses the processes, tools, and procedures to enable the recovery or continuation of vital technology infrastructure and systems following a natural or human-induced disaster.

Key Components:

• • Disaster Recovery Plan (DRP): A documented, structured approach describing how an organization can resume operations after a disaster.

  • Recovery Time Objective (RTO): The maximum acceptable length of time that the application/database can be offline.

  • Recovery Point Objective (RPO): The maximum acceptable amount of data loss measured in time (e.g., if the RPO is 1 hour, backups must be taken at least hourly).

Strategies:

• • Data Vaulting: Sending backup tapes to a secure off-site location.

  • Remote Mirroring: Maintaining a live, synchronized copy of the database at a remote site.

  • Cloud-Based Recovery: Using cloud services for backup storage and as a standby recovery site.