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Garbage collector configuration reference

The following table provides guidance for configuring the garbage collector.

Selecting the appropriate garbage collector depends on the size of the heap and available CPU resources. The following is a table of available collectors and some general guidance on when and how to use them.

Specify the garbage collector using the jvm-memory.options file located in the PA_HOME/conf directory. Modify the parameter beneath #Use the parallel garbage collector using the information provided below:

Garbage Collector Description Modifications

Parallel

  • Best used with heaps 4GB or less

  • Full stop-the-world copying and compacting collector

  • Uses all available CPUs, by default, for garbage collection

Default collector for server Java Virtual Machine (JVM). No modification is required.

Concurrent Mark Sweep (CMS)

  • Best for heaps larger than 4GB with at least 8 CPU cores

  • Mostly a concurrent collector

  • Some stop-the-world phases

  • Non-compacting

  • Can experience expensive, single threaded, full collections due to heap fragmentation

Set to ‑XX:+UseConcMarkSweepGC in the jvm-memory.options file.

Garbage First (G1)

  • Best for heaps larger than 6GB with at least 8 CPU cores

  • Combination concurrent and parallel collector with small stop-the-world phases

  • Long-term replacement for CMS collector, does not suffer heap fragmentation like CMS

Set to ‑XX:+UseG1GC in the jvm-memory.options file. Also disable #Minimum size for the Young Gen space and #Maximum size for the Young Gen space tuning. Explicit sizing adversely affects pause time goal. To disable, comment the lines out in the script.