OLAT in cluster mode requires a JMS system to be available. Since we completely rely on the JMS specification you can use any of your preferred JMS provider. Also, we don't put any special requirements on the JMS provider such as persistency or failure tolerance. Hence you could use a standalone JMS server or a serverless, multicast based JMS.
As an example we're presenting the configuration of ActiveMQ here.
Download ActiveMQ 5.2 or newer from here: http://activemq.apache.org/download.html
In conf/activemq.xml adjust the networkConnector to be static://tcp://localhost:61616
In conf/activemq.xml remove the discoveryUri from the transportConnector named 'openwire' to avoid multiple ActiveMQ servers to discover each other - unless you want exactly that
Start the ActiveMQ server via bin/activemq.bat/.sh
Configure the jms.broker.url in OLAT's build.properties accordingly