What are -Xms and -Xmx JVM parameters in java, And differences between them


In this core java tutorial we will learn What are -Xms and -Xmx JVM parameters in java, And differences between -Xms and -Xmx JVM parameters in java.

Contents of page >
  • What is -Xms JVM parameter in java?
    • Examples of using -Xms VM (JVM) option in java >
  • What is -Xmx JVM parameter in java?
    • Examples of using -Xmx VM option in java >
  • What are differences between -Xms and -Xmx JVM parameters in java?



Before learning about -Xms and -Xmx JVM parameters in java we must know about java heap memory structure.
Earlier we read about JVM Heap memory (Hotspot heap structure)  in java consists of following elements>
  1. Young Generation
    • 1a) Eden,
    • 1b) S0 (Survivor space 0)
    • 1c) S1 (Survivor space 1)
  2. Old Generation (Tenured)
  3. Permanent Generation.


What is -Xms JVM parameter in java?
-Xms : Xms is minimum heap size which is allocated at initialization of JVM in java.

Examples of using -Xms VM (JVM) option in java >
Example1 of using -Xms VM (JVM) option in java >
java -Xms512 MyJavaProgram
It will set the minimum heap size of JVM to 512 bytes.

Example2 of using -Xms VM (JVM) option in java >
java -Xms512k MyJavaProgram
It will set the minimum heap size of JVM to 512 kilobytes.

Example3 of using -Xms VM (JVM) option in java >
java -Xms512m MyJavaProgram
It will set the minimum heap size of JVM to 512 megabytes.

Example4 of using -Xms VM (JVM) option in java >
java -Xms1g MyJavaProgram
It will set the minimum heap size of JVM to 1 gigabyte.


What is -Xmx JVM parameter in java?
-Xmx : Xmx is the maximum heap size that JVM can use.

Examples of using -Xmx VM option in java >
Example1 of using -Xmx VM (JVM) option in java >
java -Xmx512 MyJavaProgram
It will set the maximum heap size of JVM to 512 bytes.

Example2 of using -Xmx VM (JVM) option in java >
java -Xmx512k MyJavaProgram
It will set the maximum heap size of JVM to 512 kilobytes.

Example3 of using -Xmx VM (JVM) option in java >
java -Xmx512m MyJavaProgram
It will set the maximum heap size of JVM to 512 megabytes.

Example4 of using -Xmx VM (JVM) option in java >
java -Xmx1g MyJavaProgram
It will set the maximum heap size of JVM to 1 gigabyte.


What are differences between -Xms and -Xmx JVM parameters in java?

-Xms JVM parameter
-Xmx JVM parameter
Xms is minimum heap size which is allocated at initialization of JVM in java.
Xmx is the maximum heap size that JVM can use.
Examples of using -Xms VM (JVM) option in java >
Example1 of using -Xms VM (JVM) option in java >
java -Xms512m MyJavaProgram
It will set the minimum heap size of JVM to 512 megabytes.

Example2 of using -Xms VM (JVM) option in java >
java -Xms1g MyJavaProgram
It will set the minimum heap size of JVM to 1 gigabyte.

Examples of using -Xmx VM option in java >
Example1 of using -Xmx VM (JVM) option in java >
java -Xmx512m MyJavaProgram
It will set the maximum heap size of JVM to 512 megabytes.

Example2 of using -Xmx VM (JVM) option in java >
java -Xmx1g MyJavaProgram
It will set the maximum heap size of JVM to 1 gigabyte.






Summary -


So in this core java tutorial we learned what are -Xms and -Xmx JVM parameters in java, And differences between -Xms and -Xmx JVM parameters in java.


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