Tracing is used when you are attempting to debug a specific feature of WebSphere. For example, let's say some issue is occurring when attempt to stop or start an application server.

In the left panel of the WebSphere admin console, expand Troubleshooting and select Logs and trace. Select the deployment manager, node agent, or application server that you want to enable tracing on. Select Diagnostic Trace. Options to configure the trace.log are displayed.

In the left panel of the WebSphere web console, expand Troubleshooting and select Logs and trace. Select the deployment manager, node agent, or application server that you want to enable tracing on. Select Change log level details. By default, the log level should be *=info.

In this example, the trace log should be located at ${SERVER_LOG_ROOT}/trace.log. Note that ${SERVER_LOG_ROOT} is a global WebSphere variable defined at Environment > WebSphere variables.

Or, the -trace flag can be used with certain commands. For example, let's say some issue is occurring when attempt to stop or start an application server. The -trace flag can be used along with the stopServer.sh and startServer.sh commands to add tracing events to trace.log.

${was_install_root}/profiles/your_profile/bin/stopServer.sh server01 -trace
${was_install_root}/profiles/your_profile/bin/startServer.sh server01 -trace