Is there any command in linux which will force linux machine to not shut-down

I have a very important process which is having a Queue, In Queue i'm storing important data and when if someone trap that process it must have to process the data which is there in the Queue after that it will terminate itself.

So if user perform a shut-down operation then that process will be killed and my data will be lossed...

So my Question is, Do we have any command which will wait or do not allow machine to shut-down, Or give your valuable alternative suggestion for handling this situation.