What happens if there is a new tick and the OnCalculate() function has not finished its calculations?

[DANZY]

I beleive if your case happened then pc (or server) will hang.
But, generally we have not yet seen operations which not performed fast by computer these days unless you have a very old pc in most case nowadays hardware is powerful enough to return the ontick before the new one.
But ... EAs are now sophisticated, often with multi currencies ... So there's exception.
Add to this that sometimes ticks arrives by packets of many hundred like during news ... And it gives good arguments to the pros ontick-nonblocking