BPMN Are catch messages queud by the system?

Question

We have long running BPM instances.
Event Sub processes are used to interact with those BPM instances
using correlation key. All this works fine in regards to having the
subprocess calling the right BPM instance and retreiving the needed information.
The question I have is: If an event subprocess is called
on a running BPM instance that already is processing the same event subprocess, would
that  second event be lost or would it be queued by the system?
We wrote a little BPM test program:
We have a dummy main BPM that is started and initialize itself with a correlation key.
We also have an event subprocess that begins with a Start Message and uses the main
BPM correlation key. At that point everything works fine.
The event subprocess consist of :
Writing a message when entering the event subprocess, sleep for 20 seconds and then write a message
when sleep is done.
Within EM we started the the main BPM instance and quickly call 2 times the
subprocess operation. To our great surprise, the subprocess where queued.
2 messages where created when entering subprocess (for the 2 calls we have made).
But as soon the timer expired, only ONE “write done sleeping” was performed.
Its like if the second token was created when entering the event subprocess, while the first token was on the
timer. But when the second token reached the timer, they merged into one token forgetting the first call.
Clearly, using this technique to interact with a running
BPM is not safe or we are doing something wrong. Is there a better way to achieve our goal?
Thanks a lot
Antoine :)

Answer 1

I found the cause of my problem,
I was not using subprocess data object in the subproces. I was using process data object so values where overwritten by the next subprocess.
Antoine :)