Concurrent Processing Server Architecture in Oracle eBusiness suite R12 is a key feature that allows non–interactive and long-running functions like reporting programs and data updating programs to be executed along with interactive operations like user is working on HTML/OAF based modules or Oracle Forms based modules/functions. Basically Concurrent processing Server simultaneously executes programs running in the background with online operations while entering data in different modules of EBS for example, you are entering invoice in payable and simultaneously you can run Payable Summary Report in background.