Transient vs. Durable Processes in Oracle BPEL

As a general practice, it is better to design your BPEL processes as transient instead of durable if performance is a concern. Note that this may not always be possible due to the nature of your process, but keep the following points in mind.

The dehydration store is used to maintain long-running asynchronous BPEL instances state information as they wait for asynchronous callbacks. This ensures the reliability of these processes in the event of server or network loss.

Oracle BPEL Process Manager supports two types of processes; Transient and Durable.

Transient Processes

Transient processes do not incur dehydration during their process execution. If an executing process experiences an unhandled fault or the server crashes, instances of a transient process do not leave a trace in the system. Thus, these instances cannot be saved in-flight regardless if they complete normally or abnormally. Transient processes are typically short-lived, request-response style processes. Synchronous processes are examples of transient processes.

Durable Processes

Durable processes incur one or more dehydration points in the database during execution. Dehydration is triggered by one of the following activities:

• Receive activity
• OnMessage branch in a pick activity
• OnAlarm branch in a pick activity
• Wait activity
• Reply activity
• checkPoint() within a bpelx:exec activity

Durable processes are typically long-living and initiated through a one-way invocation. Because of out-of-memory and system downtime issues, durable processes cannot be memory-optimized.

What should you do?

• If the design of the process allows it, design your BPEL processes as short-lived, synchronous transactions.
• If the design of the process allows it, avoid the activities listed above.

Any time your process is dehydrated to the dehydration store, this naturally impacts the performance of the process, and becomes a concern particularly in high volume environments.