How To Tell If There Is A Memory Shortage And What To Do About It

• It's not a bottleneck • Just lots of memory pressure •

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An OS memory shortage can cause bizarre and intense performance situations. In this presentation we will explore different ways to tell if there is a memory shortage and how this affects Oracle performance.

First I'll explain operating system process memory, including how to tell how much memory a process is truly consuming. Then I will introduce the OS tools we will use such as vmstat, iostat, top and sar. From an Oracle perspective I'll explain the free tools used to observe SQL statement elapsed times and the key database throughput metrics.

Then the fun starts! Using a simple shell script, I will slowly increase memory usage and we will watch what happens using the tools I previously introduced. Watching how a memory shortage affects CPU utilization, the IO subsystem as well as Oracle processes and throughput will leave an immediate and lasting impression. As you will see, a memory bottleneck (excuse me, memory pressure) can cause some truly strange performance behavior.

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