Is there any OOTB feature available in appian to update the pv variables of the inflight instances apart from IFM (In-flight Modification) plugin? please suggest.

Yes David it is the second case. That is what even i am thinking about, before that just want to explore other possible options. 

Hi Chris,

Thanks for your suggestions, i will try these options to see if it works for my design. 

Be aware that a larger number of active process instances, waiting for incoming messages, can have a severe impact on system performance and stability. I suggest to discuss your design with Appian before going on.

Totally agree with Stephan,, take into consideration the fact that having a lot of process instances waiting for messages can lead to performance issues....

I may be wrong but I think that mostly applies if you send a msg without a destination process id and it has to scan all the listeners. I would obviously strongly advise to always provide a destination process id when sending a msg event but I agree that its not fool proof and could be dangerous in some environments.

Agree, un-targeted messaging should be completely avoided in my opinion. 

With targeting by process ID, we'll have around 500 Receive Message events active at one time - that small range has not given us any concerns.  Based on what I've seen, I would feel comfortable scaling that up some if needed.