Benefits of Configuring More Memory in the IBM z/OS Software Stack

An IBM Redpaper publication


Significant performance benefits can be experienced by increasing the amount of memory assigned to various functions in the IBM® z/OS® software stack, operating system, and middleware products. IBM DB2® and IBM MQ buffer pools, dump services, and large page exploitation are just a few of the functions whose ease of use and performance can be improved when more memory is made available to them.

These benefits can include:

  • Reduced I/O operations
  • Reduced CPU usage
  • Improved transaction response time
  • Potential cost reductions

Although the magnitude of these improvements can vary widely based on a number of factors, including potential I/Os to be eliminated, resource contention, workload, configuration, and tuning, clients should carefully consider whether their environment could benefit from the addition of more memory to the software functions described in this IBM Redpaper™ publication.

This paper describes the performance implications of increasing memory in the following:

  • DB2 buffer pools
  • DB2 tuning
  • IBM Cognos® Dynamic Cubes
  • MDM with larger DB2 buffer pools
  • Java heaps and Garbage Collection tuning and Java large page use
  • MQ v8 64-bit buffer pool tuning
  • Enabling more in-memory use by IBM CICS® without paging
  • DFSort I/O reduction
  • Fixed pages and fixed large pages

Table of contents

Chapter 1. Buffer pools and related tuning
Chapter 2. Large pages
Chapter 3. New applications, analytics
Chapter 4. Other benefits of larger memory
Chapter 5. Conclusion


Publish Date
20 November 2015

Last Update
30 November 2015

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