Integrated Data Dictionary Mapping Entities › Data Dictionary Entities Used by the Mapping Compilers › Element Occurrences

Element Occurrences

What is an Element?

A record element is a logical subdivision of a record; an element cannot be addressed without first addressing the record to which the element belongs.

Element occurrences define group or elementary data items that can be used in CA-IDD-built records or CA IDMS/DB schema-built records. Elements used by maps must be defined in the dictionary and must be members of records prior to map compilation.

Establishing Element Occurrences

Element occurrences can be established in the data dictionary in one of the following ways:

• The ADD ELEMENT statement submitted to the DDDL compiler establishes a free-standing element that can be included in a CA-IDD-built record or that can be included automatically in a schema-built record.
• The RECORD statement submitted to the DDDL compiler, in conjunction with the RECORD ELEMENT substatement or the COBOL substatement, establishes a CA-IDD-built record and all elements that participate in that record. If the element specified in the substatement matches an existing element record, the existing record is used. Otherwise, a new element occurrence is created.
• The RECORD DESCRIPTION section of schema DDL submitted to the schema compiler establishes CA IDMS/DB schema-built records in the data dictionary. All elements that participate in the schema records are automatically established in the data dictionary.

Elements are the building blocks that form records. The batch and online compilers use element occurrences as they appear in records rather than as free-standing items.

How the Information is Used

Information defined for the record element in the data dictionary is used by either the batch or online compiler:

• The internal picture for the element is used to derive characteristics of the element, such as length or usage.
• The external picture for the element is used to determine the external characteristics of a field if both of the following conditions are true:
  • The external picture is defined at the element level and not overridden at the map-field level.
  • Automatic editing is enabled for the map field.
• The edit table is used by automatic editing and error-handling in editing data if both of the following conditions are true:
  • The edit table is defined at the record level and not overridden at the map-field level.
  • Automatic editing is enabled for the map field.
• The code table is used by automatic editing in encoding and decoding data if both of the following conditions are true:
  • The code table is defined at the record level and not overridden at the map-field level.
  • Automatic editing is enabled for the map field.

Considerations

An element occurrence defined in the data dictionary can be modified or deleted. The following considerations apply to the deletion of element occurrences:

• An element that participates in a record cannot be deleted.
• An element that participates in a group element structure cannot be deleted.

Critical changes to dictionary-defined record elements, such as a change in an element's picture, necessitate regenerating maps and recompiling programs that use those maps (For more information, see "Critical Changes".).