BPEL - CallBack Message Handling

BPEL engine maintains all Async call back messages into database table called dlv_message. Wecan see such all messages in BPEL console call-back manual recovery area.The query being used by bpel console is joined on dlv_message and work_item tables.This query simply picks up all call back messages which are undelivered and have not been modified with in certain threshold time.

Call-back messages are processed in following steps

• BPEL engine assigns the call-back message to delivery service
• Delivery service saves the message into dlv_message table with state 'UNDELIVERED-0'
• Delivery service schedules a dispatcher thread to process message asynchronously
• Dispatcher thread enqueues message into JMS queue
• Message is picked up by MDB
• MDB delivers the message to actual BPEL process  waiting for call-back and changes state to 'HANDLED=2'

So given above steps, there is always possibility that message is available in dlv_message table but MDB is failed in delivering it to BPEL process which keeps message always in state= 0.