Deployment Manual / Switching to G1GC

Deployment Manual / Version 2512.1

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Switching to G1GC

To switch an application to G1GC, set JAVA_PARALLEL_GC to false and pass the desired G1 tuning flags via the JAVA_OPTS environment variable (or the equivalent jvmFlags in the distroless profile). The following example, derived from field experience with high-traffic CAE deployments, is a reasonable starting point:

<environment>
  <JAVA_HEAP>16g</JAVA_HEAP> 
  <JAVA_PARALLEL_GC>false</JAVA_PARALLEL_GC> 
  <JAVA_OPTS>
    -XX:+UseG1GC
    -XX:MaxGCPauseMillis=200
    -XX:+ParallelRefProcEnabled
    -XX:InitiatingHeapOccupancyPercent=45
    -XX:ParallelGCThreads=2
    -XX:ConcGCThreads=1
  </JAVA_OPTS> 
</environment>

	Heap size for a high-traffic deployment (4 cores, 16 GB). This represents the upper end of observed production configurations. Most CAE and Headless Server deployments operate in the 4–12 GB range.
	Disables the Parallel GC activation in the entrypoint script.
	Activates G1GC and tunes pause-time target, concurrent GC threads, and heap occupancy threshold. Adjust `ParallelGCThreads` and `ConcGCThreads` to match the actual number of available CPU cores.

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