A null bitmap is used in the variable-length record format to indicate if an attribute has a null value. In rare cases, the majority of a tuple's properties are null. To minimize the cost of a null...

A null bitmap is used in the variable-length record format to indicate if an attribute has a null value. In rare cases, the majority of a tuple's properties are null. To minimize the cost of a null property to only a single bit, it is possible to change how records are represented.