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Address Space Identifier

ASID

Enhanced Definition

A unique numeric identifier assigned to each address space in a z/OS system, analogous to a UNIX Process ID (PID). The ASID enables the system to distinguish and manage different address spaces.

Key Characteristics

- 16-bit value ranging from 1 to 65535
- Unique within a z/OS image (LPAR)
- Assigned at address space creation
- Used for cross-memory services and communication
- Displayed in system monitoring tools
ASID Assignment:
- 1: Master scheduler address space
- 2-n: System address spaces (JES, VTAM, etc.)
- Dynamic: User and application address spaces
- Reusable: ASIDs recycled when address spaces terminate
ASID Usage:
- Cross-memory communication between address spaces
- Storage access across address space boundaries
- System resource management and accounting
- Performance monitoring and workload management
- Security and access control

Use Cases

- Identifying specific jobs or tasks in system displays
- Troubleshooting cross-memory access violations
- Monitoring resource consumption by address space
- Managing workload priorities and service classes
- Debugging inter-address-space communication