[TechNote] Enabling verbose garbage collection (verboseGC) in WebSphere Application Server v8.5

Enabling verbose garbage collection (verboseGC) in WebSphere Application Server

Technote (troubleshooting)

Problem(Abstract)

Enabling verboseGC output is often required when diagnosing issues with WebSphere Application Server. The following describes how to enable verboseGC output within WebSphere Application Server.

Resolving the problem

Select the appropriate version and server type:
Version 8.5, 8.0 and 7.0 - Application Servers
Version 6.1 and 6.0 - Application Servers
Version 8.5, 8.0, 7.0, 6.1, and 6.0 - Deployment Managers
Version 8.5, 8.0, 7.0, 6.1, and 6.0 - Node Agents
Version 8.5, 8.0, 7.0, and 6.1 - Enabling at Runtime


Depending on the operating system in use, the verboseGC output will be written to the following file by default:
AIX, Linux, or Windows: native_stderr.log
Solaris or HP-UX native_stdout.log

Enabling verboseGC on releases of Version 8.5, 8.0 and 7.0 - Application Servers

1. In the Administrative Console, expand Servers, expand Server Types, and then click WebSphere application servers.
   
   
2. Click on the server that you would like to work with, for example, server1.
   
   
3. On the Configuration tab, under Server Infrastructure, expand Java and Process Management, and click Process Definition.
   
   
4. Under the Additional Properties section, click Java Virtual Machine.
   
   
5. Check the Verbose Garbage Collection check box.
   
   For Solaris or HP-UX, also complete these additional steps.
   
   
6. Apply and Save the changes.
   
   
7. Restart the Application Server for the changes to take effect.
   
   

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Enabling verboseGC on releases of Version 6.1 and 6.0 - Application Servers

1. In the Administrative Console, expand Servers and then click on Application Servers.
   
   
2. Click on the server that you would like to work with, for example, server1.
   
   
3. On the Configuration tab, under Server Infrastructure, expand Java and Process Management, and click Process Definition.
   
   
4. Under the Additional Properties section, click Java Virtual Machine.
   
   
5. Check the Verbose Garbage Collection check box.
   
   For Solaris or HP-UX, also complete these additional steps.
   
   
6. Apply and Save the changes.
   
   
7. Restart the Application Server for the changes to take effect.

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Enabling verboseGC on releases of Version 8.5, 8.0, 7.0, 6.1, and 6.0 - Deployment Managers

1. In the Administrative Console, expand System Administration and then click Deployment Manager.
   
   
2. On the Configuration tab, under Server Infrastructure, expand Java and Process Management, and click Process Definition.
   
   
3. Under the Additional Properties section, click Java Virtual Machine.
   
   
4. Check the Verbose Garbage Collection check box.
   
   For Solaris or HP-UX, also complete these additional steps.
   
   
5. Apply and Save the changes.
   
   
6. Restart the Deployment Manager for the changes to take effect.

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Enabling verboseGC on releases of Version 8.5, 8.0, 7.0, 6.1, and 6.0 - Node Agents

1. In the Administrative Console, expand System Administration and then click Node Agents.
   
   
2. Click on the node agent that you would like to work with.
   
   
3. On the Configuration tab, under Server Infrastructure, expand Java and Process Management, and click Process Definition.
   
   
4. Under the Additional Properties section, click Java Virtual Machine.
   
   
5. Check the Verbose Garbage Collection check box.
   
   For Solaris or HP-UX, also complete these additional steps.
   
   
6. Apply and Save the changes.
   
   
7. Restart the Node Agent for the changes to take effect.

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Additional Steps for Solaris and HP-UX

Add the following parameters to the Generic JVM arguments:

For WebSphere Application Server 7.0 (Java 6) and later:

-XX:+PrintGCDetails
-XX:+PrintGCDateStamps
-XX:+PrintHeapAtGC

For WebSphere Application Server 6.1 (Java 5) and earlier:

-XX:+PrintGCDetails
-XX:+PrintGCTimeStamps
-XX:+PrintHeapAtGC

The -XX:+PrintHeapAtGC parameter will generate a large amount of logging to the native_stdout.log. Please ensure there is adequate file system space when enabling this option. All the information produced by this option is known to the JVM; therefore, there is no extra processing required as a result of enabling this parameter. However, there will be a slight amount of additional I/O overhead which should amount to less than 3%.

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Enabling verboseGC at Runtime - Version 8.5, 8.0, 7.0, and 6.1

Before enabling verboseGC at runtime you should follow the appropriate instructions above to enable verboseGC within your configuration. This will ensure that when the JVM is restarted verboseGC will be enabled.

1. Using the appropriate instructions above, navigate to the Java Virtual Machine page.
   
   
2. Click the Runtime tab. This tab will be present if the JVM is running.
   
   
3. Check the Verbose Garbage Collection check box.
   
   
4. Click OK.
   

Note: Verbosegc can be enabled at runtime in Version 8.5, 8.0, 7.0, and 6.1 on all operating systems; however, it will only produce meaningful output on AIX, Linux, and Windows. This is due to the fact that both Solaris and HP-UX require additional Generic JVM arguments to produce meaningful output. These additional arguments cannot be added at runtime.