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Creating a memory image of Nuclos

Create heap and thread dumps with jvisualvm – to analyse memory leaks, freezes and for support.

HOW-TO ADMINISTRATOR STAND: JUL 2026 GILT FUER NUCLOS 4.2026.X

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A memory image (heap/thread dump) helps analyse memory leaks, freezes and crashes as well as profiling. It can be created from both the Nuclos client and server.

Post-mortem first

A post-mortem image can often still be created even after OutOfMemoryExceptions have been thrown. Always try this before restarting Nuclos.

Confidentiality

A memory image contains confidential data from your application. Only share it with trusted people and encrypt it for transport if needed.

Prerequisite

You need a JDK (not a JRE!) on the relevant system. If the server runs as a Windows service, the Tomcat JVM must be started with matching JMX parameters (see Tomcat administration). Newer installers allow specifying a JMX port in development mode.

Memory image with jvisualvm

Start bin/jvisualvm (or .exe) from the JDK.
On the left under Applications, right-click the JVM instance – the server appears as Tomcat, the client as Java Web Start.
Create a Thread Dump and a Heap Dump one after another and save each as a file.

jvisualvm: create thread and heap dump.

Windows service

If the server runs as a Windows service it is not directly visible here: run it in development mode and connect via right-click on Local → Add JMX Connection… → localhost:<JMX port>.