IBM SG24-6526-00 manual Verbose garbage collection

5.4.3 Verbose garbage collection

The JVM has an option called verbose garbage collection. This means that the garbage collector outputs statistics on its activity. To activate the option, add the parameter –verbosegcto the command line arguments in the Properties window of the application server. You must keep this option separate from other options by adding a space but the sequence is not important.

The messages are sent to the standard output file, which was defined when the application was created. You can verify this setting on the General tab of the application server settings. The file name is specified in the standard output field. If it does not specify the directory, then the file is in the working directory specified on the same tab. Note that if the standard output file starts with an exclamation mark (!), then the file is overwritten at the time that the application is started. Otherwise the file is appended to.

Figure 5-19highlights the verbosegc and related parameters on the WebSphere Console’s Application Server panel.

Figure 5-19 Application Server panel of the WebSphere console showing the -verbosegc parameter

In this example, the output goes to /OrderManagement/log/stdout.txt. Since the exclamation mark (!) is placed at the beginning of the file name, it is rewritten when the application is started. If you want to save the data from a previous run, then either do not use the !, or rename the file before you restart the application.

The example in Figure 5-19shows the page scrolled down slightly so that you can see all three relevant fields. The command line arguments field is very long. In this case, the

–verbosegc parameter is at the end and appears only because the cursor was placed in the field and the End key used to move to the end of the value. For a tip on editing the command line arguments, see 5.4.4, “Static compilation” on page 127.

126Geac System21 commerce.connect: Implementation on the iSeries Server