Cooperative - Sharing Resources

Enhanced Definition

In the z/OS environment, "cooperative - sharing resources" refers to the fundamental architectural principle and the various mechanisms that enable multiple applications, logical partitions (LPARs), or entire z/OS systems to concurrently access, utilize, and manage common system resources, data, and services in a coordinated manner. This paradigm ensures high availability, scalability, and efficient utilization of expensive mainframe hardware and software assets by allowing workloads to share infrastructure.

Key Characteristics

- Centralized Resource Management: z/OS provides robust facilities like Workload Manager (WLM), Global Resource Serialization (GRS), and Storage Management Subsystem (SMS) to centrally manage and arbitrate access to shared resources across a sysplex or within a single LPAR.
- Data Integrity and Concurrency Control: Essential mechanisms such as locking (e.g., in DB2 Data Sharing, IMS Data Sharing, GRS), journaling, and recovery protocols are crucial to maintain data integrity and consistency when multiple entities access the same data concurrently.
- High Availability and Scalability: Resource sharing facilities, particularly the Coupling Facility (CF) in a Parallel Sysplex, enable multiple z/OS images to share data and control information, providing continuous availability and allowing workloads to scale across multiple systems.
- Inter-System Communication: Protocols and facilities like VTAM, APPC, Cross-System Coupling Facility (XCF), and TCP/IP facilitate seamless communication and data exchange between cooperating systems or applications.
- Dynamic Resource Allocation: Workload Manager (WLM) dynamically adjusts resource allocation (CPU, I/O, memory) based on predefined service goals, ensuring that critical workloads receive priority access to shared resources while others cooperatively share the remainder.

Use Cases

- Parallel Sysplex for Scalability and Availability: Multiple z/OS LPARs in a Parallel Sysplex share data (e.g., DB2 Data Sharing, IMS Data Sharing) and control structures via the Coupling Facility, allowing a single logical system image for applications and continuous operation even if an LPAR fails.
- Shared DASD for Data Access: Multiple z/OS systems accessing the same direct access storage devices (DASD) volumes, managed by GRS or other serialization mechanisms, to share datasets like VSAM files or PDS/PDSE libraries.
- Workload Balancing with WLM: Workload Manager distributes and manages system resources (