arango> a1 = db.example.save({ a : 1 });
{ "_id" : "116308/4042634", "_rev" : 4042634 }
arango> a2 = db._replace(a1, { a : 2 });
{ "_id" : "116308/4042634", "_rev" : 4108170, "_oldRev" : 4042634 }
arango> db._delete(a1);
JavaScript exception in file '(arango)' at 1,4: [ArangoError 1200: conflict: cannot delete document]
!db._delete(a1);
!   ^
arango> db._delete(a1, true);
true
arango> db._document(a1);
JavaScript exception in file '(arango)' at 1,4: [ArangoError 1202: document not found: document not found]
!db._document(a1);
!   ^