Controls required field checking for EntitySets and relationships with fields.
SET CHECKNULLS ON|OFF
The CHECKNULLS option is set ON by default.
When CHECKNULLS is ON, an error results if a Required field is assigned the $Null property during an ADD, CHANGE, INSERT, or UPDATE command. Normally, you should always leave CHECKNULLS set ON.
Even if you switch null checking OFF, you should always explicitly or implicitly assign some value to every required field.
Note: A field is Required if its definition in the Object Dictionary specifies yes for Reqd.