Optimizing the Java Virtual Machine

  -X Command-Line Options
  -XX Command-Line Options
  Log4j Vulnerability Optimization
  External Calls
  External Sort
  Sequential Fixed-Blocked (FB) Files
  Sequential Variable-Blocked (VB) Files
  VSAM Key Sequential Data Sets (KSDS)
  Default JVM Settings

You can set many different options that change the behavior when starting or running the Java Virtual Machine (JVM). These options are optional, but some are set as default (hidden). There are also options that must be used to prevent security leaks.
The options are command-line options and can be set in the JVM configuration script. A subset of optimization options can be found below.
Note:
Not every option is recommended or applicable for each operating system.
These options are set in the configuration script or file of the JVM directly.
Example for z/OS Java Optimization
This example uses the option -Xgcpolicy:optthruput and -Xquickstart. It is applicable for all options described in this section. You can add options by separating them with blanks.
# Configure JVM options
# Add JVM optimization parameters here
# O=to continue in next line
IJ0 ="- Xquickstart -Xgcpolicy : optthruput "
# Uncomment the following to aid in debugging " Class Not Found " problems
IJO =" $IJO -verbose : class "
export IBM_JAVA_OPTIONS =" $IJO "
//*