The SyncMaxWaitTime property applies to durable synchronous processes that are called in an asynchronous manner.

Assume you have a BPEL process with the definition shown in the following example. The process is not durable because there are no breakpoint activities.

<receive name="receiveInput" partnerLink="client" variable="input"
createInstance="yes" />
<assign>
...
</assign>
<reply name="replyOutput" partnerLink="client" variable="output" />

If a Java client or another BPEL process calls this process, the assign activity is performed and the reply activity sets the output message into a HashMap for the client (actually the delivery service) to retrieve. Since the reply is the last activity, the thread returns to the client side and tries to pick up the reply message. Since the reply message was previously inserted, the client does not wait and returns with the reply.

Assume you have a BPEL process with a breakpoint activity, as shown in the following example:

<receive name="receiveInput" partnerLink="client" variable="input"
createInstance="yes" />
<assign>
...
</assign>
<wait name="Wait1">
      <for>'PT10S'</for>
</wait>
<reply name="replyOutput" partnerLink="client" variable="output" />

While it is not recommended to have asynchronous activities inside a synchronous process, BPEL does not prevent this type of design.

When the client (or another BPEL process) calls the process, the wait (breakpoint) activity is executed. However, since the wait is processed after some time by an asynchronous thread in the background, the executing thread returns to the client side. The client (actually the delivery service) tries to pick up the reply message, but it is not there since the reply activity in the process has not yet executed. Therefore, the client thread waits for the SyncMaxWaitTime seconds value. If this time is exceeded, then the client thread returns to the caller with a timeout exception.If the wait is less than the SyncMaxWaitTime value, the asynchronous background thread then resumes at the wait and executes the reply. The reply is placed in the HashMap and the waiter (the client thread) is notified. The client thread picks up the reply message and returns.

Therefore, SyncMaxWaitTime only applies to synchronous process invocations when the process has a breakpoint in the middle. If there is no breakpoint, the entire process is executed by the client thread and returns the reply message.