4.2.5.1.2 "COBOL Language Reference" IBM Library Server

4.2.5.1.2 Indexed Organization

Each record in the file has one or more embedded keys (referred to as key data items); each key is associated with an index. An index provides a logical path to the data records, according to the contents of the associated embedded record key data items. Indexed files must be direct-access storage files. Records can be fixed-length or variable-length.

Each record in an indexed file must have an embedded prime key data item. When records are inserted, updated, or deleted, they are identified solely by the values of their prime keys. Thus, the value in each prime key data item must be unique and must not be changed when the record is updated. You tell COBOL the name of the prime key data item on the RECORD KEY clause of the FILE-CONTROL paragraph.

In addition, each record in an indexed file can contain one or more embedded alternate key data items. Each alternate key provides another means of identifying which record to retrieve. You tell COBOL the name of any alternate key data items on the ALTERNATE RECORD KEY clause of the FILE-CONTROL paragraph.

The key used for any specific input-output request is known as the key of reference.

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4.2.5.1.2 Indexed Organization

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