How to manage the Java heap space

The JobScheduler runs a Java Virtual Machine for each task that is executed.

Heap Space usage with Java 1.8

Java 1.8 changes the memory management in way that the JVM allocates heap space depending on the available physical memory (1/64).
This results in the fact that JobScheduler tasks are allocated a lot more memory than required. Typically such jobs, e.g. the JITL jobs, can be operated with 32 MB to 64 MB. However, for a server equipped with 64 GB physical memory each task will be allocated 1 GB by default.
It is therefore recommended to reduce the memory consumption by JobScheduler settings, see chapter Modify heap size settings.

By default the JVM would use 64 MB virtual memory.
Adjustments for memory consumption of jobs
- have to made if jobs require more than 64 MB.
- can be made if jobs can be operated with 32 MB, e.g. the JITL jobs for SSH connections.

The minimum memory allocation by Java can be checked with the command:
java -XX:+PrintFlagsFinal -version
The output of the command should provide a line that contains the string InitialHeapSize with the minimum heap space setting.

Java heap space usage can be modified by JobScheduler settings at job level and at a global level:
- The -Xmxsize parameter sets the maximum Java heap size
- The -Xmssize paramter sets the initial Java heap size
  - each job can be assigned an attribute to e.g. specify 64 MB memory consumption like this
    <job java_options="-Xmx64m -Xms64m">
  - The file ./config/sos.ini can be used to specify the memory consumption for all jobs like this
    [java]
    options = -Xmx64m -Xms64m
  - The file ./config/factory.ini can be used to specify memory consumption for jobs executed with Agents like this:
    [java]
    job_options = -Xmx64m -Xms64m
For more detailed information see How to increase or decrease the Java heap space