Horizontal

Key Characteristics

• • Workload Distribution: Spreading incoming transactions or requests across multiple identical application instances (e.g., CICS regions, IMS control regions, WebSphere Application Server for z/OS instances) using a load balancer or Sysplex Distributor.
  • Data Partitioning: Dividing large datasets (e.g., DB2 tables, IMS databases, VSAM files) into smaller, independent segments that can be managed, accessed, or processed concurrently across different storage units or subsystems.
  • Parallel Processing: Executing multiple batch jobs or tasks simultaneously, where each processes a distinct subset of a larger input, significantly reducing overall elapsed time for large-scale operations.
  • Increased Availability & Resilience: If one instance or partition fails, others can continue operating, often with automatic failover mechanisms, ensuring continuous service.
  • Scalability: Allows adding more instances or partitions as demand grows, providing a flexible way to scale out processing capacity without requiring a larger, more powerful single system (vertical scaling).

Use Cases

• • CICS/IMS Transaction Routing: Using a CICSplex or IMSplex with a Sysplex Distributor to route incoming transactions to multiple active CICS or IMS regions, balancing the load and providing high availability.
  • DB2 Data Sharing: Distributing data access and processing across multiple DB2 subsystems within a data sharing group, allowing concurrent updates and queries from different LPARs while maintaining data integrity.
  • Parallel Batch Processing: Dividing a large input file into multiple segments and submitting several JCL jobs concurrently, each processing a different segment, to complete a long-running batch process faster.
  • VSAM Data Set Partitioning: Creating multiple VSAM KSDS or ESDS files based on a key range or other criteria, allowing different applications or jobs to access distinct partitions concurrently without contention.
  • WebSphere Application Server for z/OS Clusters: Deploying multiple instances of WebSphere Application Server within a z/OS sysplex and using a workload manager to distribute HTTP requests horizontally across them.

Related Concepts