HPjmeter 4.3 User's Guide

Figure 17 Appearance of GC Data Collected in Intervals During a Session
NOTE: For the signal to be captured by the JVM, you must either be logged in as root, or you
must be the user who started the JVM.
Related Topics
• Using Specialized Garbage Collection Displays (page 181)
Data Collection with -Xloggc
-Xloggc directs a smaller set of data to a file than what is available with -Xverbosegc.
For every garbage collection, the following six fields are printed to the log file:
• Cumulative time since data collection began (in seconds)
• Garbage collection type
• Heap in use before the GC event
• Heap in use after the GC event
• Current maximum heap size
• Duration of the GC event
To capture basic -Xloggc data, use the following command:
$ java ... -Xloggc:filename
More data are available if you start the JVM with the -XX:+PrintGCDetails or
-XX:+PrintHeapAtGC options. For example, you can type:
100 Analyzing Garbage Collection Data