Inefficient - Poor performance

Enhanced Definition

In the z/OS context, "inefficient - poor performance" refers to a condition where a mainframe application, system component, or process consumes more system resources (CPU, I/O, memory) or takes longer to complete than necessary or expected. This leads to degraded response times for online transactions, extended durations for batch jobs, or higher operational costs due to increased resource consumption. It signifies a deviation from optimal resource utilization and throughput.

Key Characteristics

- High Resource Consumption: Excessive CPU utilization (MSUs), I/O operations (EXCPs), memory usage, or network bandwidth for a given workload or transaction.
- Extended Execution Times: Batch jobs or utilities taking significantly longer than their Service Level Agreement (SLA) or historical averages.
- Degraded Response Times: Online transactions (e.g., CICS, IMS) experiencing unacceptable delays for end-users, impacting productivity and user experience.
- Increased Monthly License Charge (MLC): Higher software costs, particularly for CPU-based licensing, directly resulting from inefficient code or processing.
- Resource Contention: Processes competing for limited system resources, leading to queuing, waits, and delays (e.g., enqueues, latch contention, buffer pool contention).
- System Bottlenecks: Identification of specific components (e.g., a particular DASD volume, a DB2 buffer pool, a CICS region, a network link) as the primary limiting factor.

Use Cases

- Batch Job Optimization: A critical overnight batch job written in COBOL that used to complete in 2 hours now consistently takes 6 hours, delaying subsequent dependent jobs and impacting online system availability.
- Online Transaction Response: CICS transactions for a specific application are consistently exceeding 2-second response times, leading to user complaints and potential SLA breaches.
- DB2 Query Tuning: A newly deployed SQL query within a COBOL application is causing high CPU usage and long execution times in DB2, impacting the entire subsystem's performance.
- I/O Subsystem Analysis: Excessive I/O waits reported by RMF for a particular set of VSAM data sets, indicating potential contention, inefficient data access patterns, or poor dataset placement.
- Memory Leak Detection: A long-running started task or CICS region shows a continuous, unexplained increase in private storage usage over time, eventually leading to abends or performance degradation.

Related Concepts

Inefficient performance is often a symptom of underlying issues related to application design (e.g., poorly written COBOL code, unoptimized SQL), system configuration (e.g., insufficient buffer pools, incorrect dataset placement, WLM policy misconfiguration), or data management (e.g., fragmented VSAM files, missing DB2 indexes). It directly impacts Service Level Agreements (SLAs), operational costs, and system stability. Tools like SMF (System Management Facilities), RMF (Resource Measurement Facility), and specialized performance monitors (e.g., Omegamon, Strobe, CA-DPM) are crucial for identifying, diagnosing, and resolving performance inefficiencies, often leading to performance tuning efforts.

Best Practices:

Proactive Monitoring: Implement robust, continuous monitoring using tools like RMF, SMF, and specialized performance monitors to detect performance deviations and potential bottlenecks early.
Regular Performance Reviews: Conduct periodic reviews of key workloads (batch, online, utility) to identify trends, analyze historical data, and anticipate potential performance issues before they become critical.
Code Optimization: Encourage developers to write efficient COBOL, PL/I, or Assembler code, and to optimize SQL queries using tools like EXPLAIN in DB2 and access path analysis.
Dataset and Storage Management: Optimize dataset placement across DASD volumes, select appropriate block sizes, and utilize