Want to discuss with you the case of %Status.
If you familiar with ObjectScript you know what is it. I'd love to hear the history of the case why it had appeared in ObjectScript but it turned out that almost every system/library classmethods return %Status and there is a whole set of tools to deal with it.
What is does it gives you the responsibility to check the value or %Status of every system method you call.
E.g. if you save the data of the persistent class, you should never call like this:
you need to call:
set sc=obj.%Save() if $$$ISERR(sc) do // something or quit.