Relativity provides the facility to define custom data types for SQL column descriptions. Relativity custom data types are similar to domains in some relational database management systems. A custom data type allows you a quick way to apply a common set of characteristics to one or more columns - those characteristics include the data type, length, default value, whether the column allows null values, whether the column is constrained to certain values, and, for numeric type columns, the precision and scale.
Using custom data types can add consistency to your tables. They also make it easy to adjust column properties, as you only have to make the required changes in one place, instead of having to edit each individual column that shares a particular type. Custom data types, once defined, can be associated with a COBOL data item as the default type to use when a column is based on that data item.