The DD and ALIAS Options
The DD option or the ALIAS option is used to reference alias (alternate) names. The specification of an alias name in DDS allows a data name of up to 30 characters to be included in the COBOL program.
When the DD option or the ALIAS option is used, any alias names present replace the corresponding DDS field names. All underscores in the alias names are translated into hyphens before any replacing occurs.