Figure 7-4. TurboIMAGE/XL Data Set Organization Example

Automatic Master Set

The characteristics of an automatic master set are: Each data entry contains a chain head.

A data entry (record, in MPE/iX terms) can con tain only the k ey item used as an index pointer.

TurboIMAGE/XL automatically updates the master set when modi￿cations are made to the related detail sets. Changing a searc h item requires deleting the old one and adding the new one. The master set is automatically done.

Use of an automatic master set sa ves time when key item values are unpredictable or so numerous that it is not expedien t to make manual additions and deletions of master data entries. However, it may introduce data redundancy.

Manual Master Set

A manual master set data en try can contain not only a k ey item, but additional data items that provide information in addition to the k ey item. The characteristics of a man ual master set are:

Each data entry contains a chain head.

You must explicitly add or delete all data en tries.

You must add a key item in a master set data en try before adding a related detail set data entry.

You must delete all related detail sets before adding a master set en try. Allows control over data entries that an automatic master set does not.

Data Management 7-13