For information on converting to InterSystems IRIS, see the
InterSystems IRIS Adoption Guide
and the InterSystems IRIS In-Place Conversion Guide,
both available on the WRC Distributions page (login required).
Method to Check foreign key for existence. If lock is TRUE then the object referenced by
the key value is also locked. If the reference does not exist or, if locking is requested and the lock fails
then an error message is returned.