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

Mark Wisniewski · Brenda Beane · David Betten · Clark Goodrich · Akiko Hoshikawa · David Herr · Catherine Moxey · Tony Sharkey · Pete Siddall · Robin Tanenbaum · Elpida Tzortzatos · David L Zhang · IBM Redbooks

feb 2017 · IBM Redbooks

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Significant performance benefits can be realized by increasing the amount of memory that is 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 usage are just a few of the functions whose ease of use and performance can be improved when more memory is made available to them.
The following benefits can realized:

• 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 several factors, including potential I/Os to be eliminated, resource contention, workload, configuration, and tuning, clients must carefully consider whether their environment can benefit from the addition of memory to the software functions that are described in this IBM RedpaperTM publication.
This paper describes the performance implications of increasing memory in the following areas:

• 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
  
• TCP/IP FTP
  
• DFSort I/O reduction
  
• Fixed pages and fixed large pages