When you enable the command-line option -Xdiagnosticscollector, a diagnostics configuration check runs at Java™ VM start up. If any settings disable key Java diagnostics, a warning is reported.
The aim of the diagnostics configuration check is to avoid the situation where a problem occurs after a long time, but diagnostics are missing because they were inadvertently switched off. Diagnostic configuration check warnings are reported on stderr and in the Diagnostics Collector log file. A copy of the log file is stored in the java.check.<timestamp>.<pid>.zip output file.
If you do not see any warning messages, it means that the Diagnostics Collector has not found any settings that disable diagnostics. The Diagnostics Collector log file stored in java.check.<timestamp>.<pid>.zip gives the full record of settings that have been checked.
For extra thorough checking, the Diagnostics Collector can trigger a Java dump. The dump provides information about the command-line options and current Java system properties. It is worth running this check occasionally, as there are command-line options and Java system properties that can disable significant parts of the Java diagnostics. To enable the use of a Java dump for diagnostics configuration checking, set the config.check.javacore option to true in the settings file. For more information, see Diagnostics Collector settings.
For all platforms, the diagnostics configuration check examines environment variables that can disable Java diagnostics. For reference purposes, the full list of current environment variables and their values is stored in the Diagnostics Collector log file.
Checks for operating system settings are carried out on Linux® and AIX. On Linux, the core and file size ulimits are checked. On AIX®, the settings fullcore=true and pre430core=false are checked, as well as the core and file size ulimits.