Use this page to view and change the Java virtual machine (JVM) configuration for the application server's process.
To view this administrative console page, click Servers > Application Servers > server_name > Server Infrastructure > Process Definition > Java Virtual Machine.
Configuration tab
Specifies the standard class path in which the Java virtual machine code looks for classes.
Enter each classpath entry into a table row. You do not need to add the colon or semicolon at the end of each entry.
Data type | String |
Units | Class path |
Specifies bootstrap classes and resources for JVM code. This option is only available for JVM instructions that support bootstrap classes and resources. You can separate multiple paths by a colon (:) or semi-colon (;), depending on operating system of the node.
Data type | String |
Specifies whether to use verbose debug output for class loading. The default is not to enable verbose class loading.
Data type | Boolean |
Default | false |
Specifies whether to use verbose debug output for garbage collection. The default is not to enable verbose garbage collection.
Data type | Boolean |
Default | false |
Specifies whether to use verbose debug output for native method invocation. The default is not to enable verbose Java Native Interface (JNI) activity.
Data type | Boolean |
Default | false |
Specifies the initial heap size available to the JVM code, in megabytes.
Increasing the minimum heap size can improve startup. The number of garbage collection occurrences are reduced and a 10% gain in performance is realized.
Increasing the size of the Java heap improves throughput until the heap no longer resides in physical memory, in general. After the heap begins swapping to disk, Java performance suffers drastically.
Data type | Integer |
Default | ![]() ![]() ![]() |
Specifies the maximum heap size available to the JVM code, in megabytes.
Increasing the heap size can improve startup. By increasing heap size, you can reduce the number of garbage collection occurrences with a 10% gain in performance.
Increasing the size of the Java heap usually improves throughput until the heap no longer resides in physical memory. When the heap size exceeds the physical memory, the heap begins swapping to disk which causes Java performance to drastically decrease. Therefore, it is important to set the maximum heap size to a value that allows the heap to be contained within physical memory.
To prevent paging, you should allow a minimum of 256MB of physical memory for each processor and 512 MB of physical memory for each application server. If possible, adjust the available memory when paging occurs if processor utilization is low because of this paging.
Data type | Integer |
Default | ![]() ![]() ![]() |
This setting only applies to the base WebSphere Application Server and the WebSphere Application Server - Express products. It specifies whether to use HProf profiler support. To use another profiler, specify the custom profiler settings using the HProf Arguments setting. The default is not to enable HProf profiler support.
If you set the Run HProf property to true, then you must specify command-line profiler arguments as values for the HProf Arguments property.
Data type | Boolean |
Default | false |
This setting only applies to the base WebSphere Application Server and the WebSphere Application Server - Express products. It specifies command-line profiler arguments to pass to the JVM code that starts the application server process. You can specify arguments when HProf profiler support is enabled.
HProf arguments are only required if the Run HProf property is set to true.
Data type | String |
Specifies whether to run the JVM in debug mode. The default is not to enable debug mode support.
If you set the Debug Mode property to true, then you must specify command-line debug arguments as values for the Debug Arguments property.
Data type | Boolean |
Default | false |
Specifies command-line debug arguments to pass to the JVM code that starts the application server process. You can specify arguments when Debug Mode is enabled.
Debug arguments are only required if the Debug Mode property is set to true. If you enable debugging on multiple application servers on the same server, make sure that the servers are using different address arguments, which define the port for debugging. For example, if you enable debugging on two servers and leave the default debug port for each server as address=7777, the servers could fail to start properly.
Data type | String |
Units | Java command-line arguments |
Specifies command line arguments to pass to the Java virtual machine code that starts the application server process.
The -Xquickstart option is not supported on OS/400.
The -Xverify:none option is not supported on OS/400.
The -Xgcthreads option is not supported on OS/400.
The -Xnocompactgc option is not supported on OS/400.
The -Xinitsh option is not supported on OS/400.
The -Xgpolicy option is not supported on OS/400.
The -XX option is not supported on OS/400.
The -server | -client option is not supported on OS/400.
Data type | String |
Units | Java command line arguments |
Specifies a full path name for an executable JAR file that the JVM code uses.
Data type | String |
Units | Path name |
Specifies whether to disable the just in time (JIT) compiler option of the JVM code.
If you disable the JIT compiler, throughput decreases noticeably. Therefore, for performance reasons, keep JIT enabled.
Data type | Boolean |
Default | false (JIT enabled) |
Recommended | JIT enabled |
Specifies JVM settings for a given operating system. .
When started, the process uses the server's JVM settings for the operating system.
Data type | String |
Related concepts
Java virtual machines (JVMs)
Related tasks
Using the JVM
Tuning the application serving environment
Related reference
Custom property collection