enhance process concurrency versus thread concurrency ----------------------------------------------------- Key: JBPM-461 URL: http://jira.jboss.com/jira/browse/JBPM-461 Project: JBoss jBPM Issue Type: Task Components: Training Reporter: Tom Baeyens Assigned To: Tom Baeyens 1) explain databases: what, why and show the db in a clustered j2ee architecture. include explanation about database connections, how they are related to transaction logs and why locking and concurrency is important for dbs 2) explain the jbpm data model: process definition information & process execution information 3) process executions are state machines. state changes are atomic operations. show how collisions can occur in case of concurrent updates to process executions. a) with a process variable, b) with token synchronization. both of these examples should be based on the fact that they first read the same data and then going to update it. 4) then show a picture with a server (with jbpm) and a db: on the one hand, server gets many simultanious requests. on the other hand, process execution operations should be made atomic.