This option is available only for details stereotyped attribute on an entity class.
It determines whether NULL values are permitted on the corresponding database field. Setting this option to no causes a Not Null qualifier to be included with this field in the generated DDL script.
The default value for this option is dependent on the underlying data type of the field. The default value of this option for the attributes for fields of type SVR_BOOLEAN, SVR_CHAR, SVR_FLOAT, SVR_DOUBLE, SVR_MONEY, SVR_INT8, SVR_INT16, SVR_INT32 is no.
The default value of this option for the attributes of type SVR_BLOB, SVR_DATE, SVR_DATETIME, SVR_STRING, SVR_INT64 is yes.
This topic is dealt with in Null Considerations.