How do I set Java s min and max heap size through environment variables

Question

How do I set Java s min and max heap size through environment variables   I know that the heap sizes can be set when launching java  but I would like to have this adjusted through environment variables on my server

User · Answer

If you want any java process  not just ant or Tomcat  to pick up options like -Xmx use the environment variable  JAVA OPTIONS   In bash  export  JAVA OPTIONS  -Xmx1g

User · Answer

A couple of notes    Apache ant doesn t know anything about JAVA OPTS  while Tomcat s startup scripts do  For Apache ant  use ANT OPTS to affect the environment for the JVM that runs  ant   but not for the things that ant might launch  The maximum heap size you can set depends entirely on the environment  for most 32-bit systems  the maximum amount of heap space you can request  regardless of available memory  is in the 2GiB range  The largest heap on a 64-bit system is  really big   Also  you are practically limited by physical memory as well  since the heap is managed by the JVM and you don t want a lot of swapping going on to the disk  For server environments  you typically want to set -Xms and -Xmx to the same value  this will fix the size of the heap at a certain size and the garbage collector has less work to do because the heap will never have to be re-sized

User · Answer

You can t do it using environment variables  It s done via  non standard  options  Run  java -X for details  The options you re looking for are -Xmx and -Xms  this is  initial  heap size  so probably what you re looking for

User · Answer

You can use JAVA TOOL OPTIONS   Example    export JAVA TOOL OPTIONS -Xmx512m   It has been mentioned in some comments  and in another answer   The OP s question is quite old  but as it is the first google result for the question  I thought i would add the answer here for clarity s sake

User · Answer

You can t do it using environment variables  It s done via  non standard  options  Run  java -X for details  The options you re looking for are -Xmx and -Xms  this is  initial  heap size  so probably what you re looking for

User · Answer

I think your only option is to wrap java in a script that substitutes the environment variables into the command line

User · Answer

A couple of notes    Apache ant doesn t know anything about JAVA OPTS  while Tomcat s startup scripts do  For Apache ant  use ANT OPTS to affect the environment for the JVM that runs  ant   but not for the things that ant might launch  The maximum heap size you can set depends entirely on the environment  for most 32-bit systems  the maximum amount of heap space you can request  regardless of available memory  is in the 2GiB range  The largest heap on a 64-bit system is  really big   Also  you are practically limited by physical memory as well  since the heap is managed by the JVM and you don t want a lot of swapping going on to the disk  For server environments  you typically want to set -Xms and -Xmx to the same value  this will fix the size of the heap at a certain size and the garbage collector has less work to do because the heap will never have to be re-sized

User · Answer

I think your only option is to wrap java in a script that substitutes the environment variables into the command line

User · Answer

If you want any java process  not just ant or Tomcat  to pick up options like -Xmx use the environment variable  JAVA OPTIONS   In bash  export  JAVA OPTIONS  -Xmx1g

User · Answer

You can t do it using environment variables  It s done via  non standard  options  Run  java -X for details  The options you re looking for are -Xmx and -Xms  this is  initial  heap size  so probably what you re looking for

User · Answer

Actually  there is a way to set global defaults for Sun s JVM via environment variables   See How to set a java system property so that it is effective whenever I start JVM without adding it to the command line arguments

User · Answer

I think your only option is to wrap java in a script that substitutes the environment variables into the command line

User · Answer

You can t do it using environment variables directly  You need to use the set of  non standard  options that are passed to the java command  Run  java -X for details  The options you re looking for are -Xmx and -Xms  this is  initial  heap size  so probably what you re looking for    Some products like Ant or Tomcat might come with a batch script that looks for the JAVA OPTS environment variable  but it s not part of the Java runtime   If you are using one of those products  you may be able to set the variable like     set JAVA OPTS  -Xms128m -Xmx256m      You can also take this approach with your own command line like     set JAVA OPTS  -Xms128m -Xmx256m    java   JAVA OPTS  MyClass

User · Answer

You can use JAVA TOOL OPTIONS   Example    export JAVA TOOL OPTIONS -Xmx512m   It has been mentioned in some comments  and in another answer   The OP s question is quite old  but as it is the first google result for the question  I thought i would add the answer here for clarity s sake

User · Answer

You can t do it using environment variables directly  You need to use the set of  non standard  options that are passed to the java command  Run  java -X for details  The options you re looking for are -Xmx and -Xms  this is  initial  heap size  so probably what you re looking for    Some products like Ant or Tomcat might come with a batch script that looks for the JAVA OPTS environment variable  but it s not part of the Java runtime   If you are using one of those products  you may be able to set the variable like     set JAVA OPTS  -Xms128m -Xmx256m      You can also take this approach with your own command line like     set JAVA OPTS  -Xms128m -Xmx256m    java   JAVA OPTS  MyClass

User · Answer

You can t do it using environment variables directly  You need to use the set of  non standard  options that are passed to the java command  Run  java -X for details  The options you re looking for are -Xmx and -Xms  this is  initial  heap size  so probably what you re looking for    Some products like Ant or Tomcat might come with a batch script that looks for the JAVA OPTS environment variable  but it s not part of the Java runtime   If you are using one of those products  you may be able to set the variable like     set JAVA OPTS  -Xms128m -Xmx256m      You can also take this approach with your own command line like     set JAVA OPTS  -Xms128m -Xmx256m    java   JAVA OPTS  MyClass

User · Answer

You can t do it using environment variables  It s done via  non standard  options  Run  java -X for details  The options you re looking for are -Xmx and -Xms  this is  initial  heap size  so probably what you re looking for

User · Answer

You can t do it using environment variables directly  You need to use the set of  non standard  options that are passed to the java command  Run  java -X for details  The options you re looking for are -Xmx and -Xms  this is  initial  heap size  so probably what you re looking for    Some products like Ant or Tomcat might come with a batch script that looks for the JAVA OPTS environment variable  but it s not part of the Java runtime   If you are using one of those products  you may be able to set the variable like     set JAVA OPTS  -Xms128m -Xmx256m      You can also take this approach with your own command line like     set JAVA OPTS  -Xms128m -Xmx256m    java   JAVA OPTS  MyClass

User · Answer

I think your only option is to wrap java in a script that substitutes the environment variables into the command line

User · Answer

Actually  there is a way to set global defaults for Sun s JVM via environment variables   See How to set a java system property so that it is effective whenever I start JVM without adding it to the command line arguments

[java] How do I set Java's min and max heap size through environment variables?

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