Full Backup

Enhanced Definition

A full backup in the z/OS environment involves creating a complete copy of all selected data, whether it's an entire volume, a set of datasets, or a database. Its primary purpose is to provide a comprehensive point-in-time snapshot that can be used for complete data recovery in the event of data loss, corruption, or disaster.

Key Characteristics

- Copies all data specified for the backup, regardless of whether it has changed since the last backup.
- Typically requires the most storage space and the longest time to complete compared to other backup types.
- Simplifies the recovery process, as only the full backup needs to be restored to bring the data back to the state it was in at the time of the backup.
- Often performed using z/OS utilities like DFSMSdss (Data Set Services), DFSMShsm (Hierarchical Storage Manager), or third-party backup software.
- Can be performed at the logical level (individual datasets, VSAM clusters, DB2 table spaces) or at the physical level (entire DASD volumes).
- Crucial component of any robust Disaster Recovery Plan (DRP) and Business Continuity strategy.

Use Cases

- Disaster Recovery: Creating a baseline for recovering an entire system, critical applications, or databases after a catastrophic event.
- System Migration/Upgrade: Backing up critical system volumes or application data before major operating system upgrades, hardware migrations, or software changes.
- Application Baseline: Establishing a known good state of an application's data before implementing significant code changes or new features.
- Archiving: Preserving historical data for compliance, auditing, or long-term retention purposes, often moved to tape or cloud storage.
- Data Replication: Used as the initial copy for setting up data replication solutions, where subsequent changes are then synchronized incrementally.

Related Concepts

Full backups are foundational to data protection and are often contrasted with Incremental Backups (which only copy data changed since the last backup of any type) and Differential Backups (which copy data changed since the last full backup). They are managed by DFSMS components like DFSMSdss for direct volume/dataset copying and DFSMShsm for automated, policy-driven backup and recovery. A full backup is a critical element of a Disaster Recovery Plan, ensuring Data Availability and Business Continuity by providing a complete recovery point.

Best Practices:

Schedule Strategically: Perform full backups during periods of low system activity to minimize impact on online transactions and batch processing.
Verify Integrity: Regularly test the recoverability of full backups to ensure data integrity and the validity of the backup process.
Off-site Storage: Store at least one copy of critical full backups off-site to protect against site-wide disasters.
Automate and Monitor: Automate the full backup process using JCL and scheduling tools, and implement robust monitoring to detect failures promptly.
Document Recovery Procedures: Maintain clear, up-to-date documentation for restoring data from full backups, including JCL examples and step-by-step instructions.