The purpose of setting the JVM custom property com.ibm.websphere.nodeagent.bootstrap.maxthreadpool = 5 on the node agent is to start five application server processes in parallel. This property controls the number of threads that can be included in a newly created thread pool, where each thread is dedicated to starting an application server Java virtual machine (JVM). As a result, the JVMs with dedicated threads in this thread pool are started in parallel whenever the node agent starts, allowing for up to five application server processes to start simultaneously.