The Big Picture

• Master File: Major collection of data pertaining to a specific application. Must be sorted by a "key" field.
• Transaction file: Batch data to be used for updating the "Master" file. Contains all changes that have occured since "Master" was created or last updated. Must be sorted by a "key" field.
• Master and Trans. files must be in sequence by the same key field.

Update Logic

 IF TRANS-KEY = MASTER-KEY
    Update the Master Record
 IF TRANS-KEY > MASTER-KEY
    Move the Master record to New-Master File
 IF TRANS-KEY < MASTER-KEY
    Add the Trans. record to the master record