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Greater Memory Already Making a Great Impact

August 30, 2016

In November 2015 I wrote about the launch of DB2 12 for z/OS ESP, citing all the various enhancements DB2 has made by exploiting significantly greater amounts of available memory. Well, it isn't just DB2 12 that will benefit from additional memory to reduce CPU cost.

I’ve been working with my colleague Robert Catterall, who's doing reviews with customers to see how their current systems are configured and if memory is being exploited to save MIPS. This work is based on a series of blog posts Robert wrote on trading memory for MIPS (see Part 1, Part 2, Part 3).

I like Robert's suggested rule of thumb: for each CPU engine with latest z13, you should have 20GB of real memory storage available. A single z13 CPU engine has 1,695 MIPS.

I also recently came across an IBM Redpaper titled, “Benefits of Configuring More Memory in the IBM z/OS Software Stack.”

This document discusses how larger memory is being used to help not just DB2 buffer pools and related tuning, but also MQ, Communication Server, Java, Cognos Dynamic Cubes, CICS and DFSORT.

This vast expansion of memory is welcome, because it's giving us I/O avoidance. That is, if I can store data that's referenced repeatedly in memory, then I can avoid the CPU costs associated with doing the I/O to disk. And for even greater CPU MIPS reduction, IBM introduced 1MB and 2GB page frames. This takes advantage of the large frame area (LFAREA) to reduce CPU costs associated with doing memory lookups for the getpages that are requested data from virtual storage. The LFAREA is setup using the IEASYSxx z/OS system parameters that are typically set by your z/OS systems programmer.

Systems once configured with megabytes of memory are now being configured with gigabytes of memory with systems configured with terabytes of memory. The latest z13 supports up to 10TB of memory. You've heard all about Big Data? I believe we're now entering a world of Big Memory.

Posted August 30, 2016| Permalink