6.3.1 Formula for calculating virtual memory usage

The formula for calculating (Unit: Megabytes) virtual memory usage is as follows:

Virtual-memory-usage-of-batch-server = A + B + C + (D + 10) × E + F + G

Legend:

• A: Java heap size

  The default value is the value specified in the -Xms option when invoking JavaVM. This value is extended up to the maximum value specified in the -Xmx option when invoking JavaVM on running J2EE server.

• B: Metaspace area size

  The default value is the value allocated by JavaVM. When J2EE server is running, this value increases to a maximum of the value specified in the -XX:MaxMetaspaceSize option when JavaVM started.

• C: Area size used by native program

  The value used differs for each OS. The following table describes the value of the area size used by native program for each OS:

  Table 6‒7: List of values of the area size used by native program

  OS type	Value of area used (unit: megabytes)
  Windows	300
  AIX	400
  Linux	600

• D: Number of batch server threads

  Number of threads used by the batch server. For details about the number of threads used by batch server, see 6.2.1 Estimating the resources used by batch server.

• E: Stack area size

  This is the value specified in the -Xss option when invoking JavaVM.

• F: Explicit heap size

  This is the size of the Explicit heap used in the Explicit Memory Management functionality. This value can be extended up to the maximum value specified in -XX:HitachiExplicitHeapMaxSize when invoking JavaVM on running J2EE server. Note that by default Explicit heap is invalid.

• G: Maximum size of the code cache area

  Specify this value in the -XX:ReservedCodeCacheSize option, when invoking JavaVM.

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