This field is to allow the definition of a format mask for end user tools. It does not affect the physical table definition, but rather provides input to the view ws_admin_v_dim_col which can be used to assist in the population of an end user tool's end user layer. As such it is a free form entry and any characters are valid. Typically format masks are only used on numeric fields. Example: #,###0.00. It is not worth the effort of populating this field unless it can be utilized by the end user tools in use.