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The objective of the Diagnostics Collector tool is to make it easier for you to collect all the Java diagnostics files for a problem event.
Collecting diagnostics from Java runtime problems
The Diagnostics Collector produces an output file for problem events that occur in your Java application.
When you add the command-line option -Xdiagnosticscollector, the Diagnostics Collector runs and produces several output .zip files. One file is produced at startup. Another file is produced for each dump event that occurs during the lifetime of the JVM. For each problem event that occurs in your Java application, one .zip file is created to hold all the diagnostics for that event. For example, an application might have multiple OutOfMemoryErrors but keep on running. Diagnostics Collector produces multiple .zip files, each holding the diagnostics from one OutOfMemoryError.
The Diagnostics Collector copies files that it writes to the output .zip file. It does not delete the original diagnostics information.
When the Diagnostics Collector finds a system dump for the problem event, then by default it runs jextract to post-process the dump and gather context information This information enables later debugging. Diagnostics Collector automates a manual step that is requested by IBM support on most platforms.
Verifying your Java diagnostics configuration
When you enable the command-line option -Xdiagnosticscollector, a diagnostics configuration check runs at Java VM start up. 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. If the diagnostics configuration check detects any settings that disable key Java diagnostics, a warning is reported.
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.
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.
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