Key Types

Each index element contains a particular type of key that is used for accessing records in the data file. The following table describes the full and partial keys of each type:

Table 230 Key Types

Key	Description
V	Used to index volume records in the Data file. One index element containing one V‑type key is created for each volume record in the Data file. The full V‑type key for each volume record is the full volume serial number. This is a unique key.
D	Index to dataset records in the Data file. One index element containing one D‑type key is created for each dataset record in the Data file. The full D‑type key for each dataset record is the full dataset name. Because duplicate dataset names may exist in the media library, this is a non‑unique key (that is, more than one index element may exist with the same D‑type key).
L	Index to dataset records in the Data file. An element with an L‑type key is created for each volume on which a specific dataset resides. For example, if a dataset record indicates that the dataset spans three volumes, three L‑type keys (one for each volume) are created to reference that dataset record. The full L‑type key is comprised of the full volume serial number and the full file sequence number (label) of the dataset on the volume. This is a unique key.

Key

Description

Used to index volume records in the Data file. One index element containing one V‑type key is created for each volume record in the Data file. The full V‑type key for each volume record is the full volume serial number. This is a unique key.

Index to dataset records in the Data file. One index element containing one D‑type key is created for each dataset record in the Data file. The full D‑type key for each dataset record is the full dataset name. Because duplicate dataset names may exist in the media library, this is a non‑unique key (that is, more than one index element may exist with the same D‑type key).

Index to dataset records in the Data file. An element with an L‑type key is created for each volume on which a specific dataset resides. For example, if a dataset record indicates that the dataset spans three volumes, three L‑type keys (one for each volume) are created to reference that dataset record. The full L‑type key is comprised of the full volume serial number and the full file sequence number (label) of the dataset on the volume. This is a unique key.

Depending on the function being performed when accessing the Index file, you can specify a full key or a partial key. For more information, see Index File Contents.

A partial key is shorter than the full length of the key in the index file. The most common usage of a partial key is the specification of a prefix (for example, dataset name prefix instead of a full dataset name). Partial keys can also be used when all necessary information is not available.

All index elements have the same fixed length, which is determined by the index elements with D‑type keys because the D‑type key is the longest full key (that is, the dataset name).

Index element length exceeds the length of the longest key because index elements contain additional bytes that are used by the Control‑M/Tape Repository-handling mechanisms.

Index elements with V‑type keys are mapped using assembler macro CTTDVX. Index elements with D‑type keys are mapped using assembler macro CTTDDX. Index elements with L‑type keys are mapped using assembler macro CTTDLX.

Parent Topic

Media Database Structure