Group Trailer Fields
A group trailer field provides an optional way to allow for future additions to the end of a group field. (A group field is a concatenation of fields that can be referenced together by a single field name: the group header field. See the Group Fields section for a discussion of group characteristics.) All fields within a group must have a sequence number that falls between the number you defined for the group header field and that of the field you entered in the Thru Field Name specification.
A group trailer simplifies group field maintenance by providing a placeholder to mark the end of a group. You enter a group trailer field (rather than the final field in a group) in the Thru Field Name specification on the group header field. In the future, any field you add with a sequence number between that of the group header and the group trailer becomes part of the group. It is not necessary to modify the Thru Field Name specification to include the new field.
For example, assume your account number is a group field that is currently composed of a main account, sub account, and division. If you do not use a group trailer, you must identify the division as the final field in the group (with the Thru Field Name specification). If you add a branch component to the end of the account number, you must change the Thru Field Name specification to list the branch, rather than the division, as the final field in the group. If instead, you had used a group trailer as the final field in the group, you could add a branch to the group simply by creating the branch field with a sequence number that is greater than that of the division and smaller than that of the group trailer. You would not be required to alter the Thru Field Name specification.
As with a group header field, the group trailer occupies no physical space in the file. There are no specifications that are unique to a group trailer field.
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