IAS Performance and Tuning Guide

This manual provides guidelines for system managers to improve the performance, throughput, and response time of an IAS system. It covers several areas for tuning:

• System Generation: Strategies for selecting features to optimize memory usage, including memory management directives, terminal handler configuration, batch streams, and SCOM (System Communication Area) size.
• Memory Management: Guidance on system size, managing terminal resources, and the efficient installation of tasks and handlers.
• Disk Usage: Recommendations for effective disk utilization, including placing spooler and work files on less frequently used disks, using the Disk Save and Compress (DSC) utility, and configuring swap file locations to minimize I/O contention.
• File System Tuning: Techniques to improve file system performance, such as selecting the appropriate Ancillary Control Processor (ACP) task (FCP.TSK, BIGFCP.TSK, or RESFCP.TSK), using multiple ACP tasks to enable concurrent file operations, and adjusting disk access parameters like directory LRU cache, default file extensions, and window block sizes.
• IAS Scheduler Tuning: Adjustments to scheduler parameters based on job characteristics (interactive, batch, real-time, compute-bound, or I/O-bound). It details quantum and promotion time parameters, batch scheduling, and the effects of these changes.
• Case Study: A chapter provides an example of tuning a specific system, demonstrating the impact of parameter adjustments on performance.
• Appendix: Includes a workbook for system managers to track system components, default values, and manual tuning changes.