Continuous Operation - 24/7 Availability

Enhanced Definition

In the mainframe context, **Continuous Operation - 24/7 Availability** refers to the capability of an IBM z/OS system and its associated applications and data to remain fully operational and accessible around the clock, every day of the week, with minimal to no planned or unplanned downtime. This is a fundamental requirement for mission-critical enterprise workloads that demand uninterrupted service.

Key Characteristics

- High Availability (HA): Achieved through redundant hardware components (e.g., multiple CPUs, I/O paths, power supplies), software configurations (e.g., Sysplex), and data replication, ensuring services continue even if a component fails.
- Fault Tolerance: The system's inherent ability to detect and automatically recover from component failures (hardware or software) without interrupting ongoing operations or compromising data integrity.
- Disaster Recovery (DR) Capabilities: Comprehensive strategies and technologies (e.g., GDPS) to restore full system functionality and data access rapidly following a major site-wide or regional disaster.
- Scalability and Elasticity: The ability to dynamically adjust processing capacity and resources to meet fluctuating workload demands without requiring system restarts or service interruptions.
- Non-Disruptive Maintenance: The capacity to perform routine maintenance, upgrades, and patching of hardware and software components (e.g., z/OS, CICS, DB2) without impacting active user sessions or batch processing.
- Data Integrity and Consistency: Mechanisms to ensure that data remains accurate, consistent, and recoverable across all system components, even during failures or recovery processes.