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IMS Dynamic DEDB Extensions

Category: IMS
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IMS legacy systems reliably serve the core business processes in many of the world's largest corporations. Indeed, IMS supports a variety of business applications that directly affect customers through automated teller machines, credit card transactions, airline and hotel reservations, package tracking and delivery as well as ordinary financial accounting and billing systems. Web-based applications are enriching their content by tapping into these treasure troves of data. The high availability and performance demands of these types of continuously available applications are ably met by IMS Fast Path structures called Data Entry Databases (DEDBs).

The DEDB's partitioning architecture provides the high storage capacity and operational flexibility necessary for continuous online activity. This enduring quality affords IMS application designers a ready alternative to any artificial partitioning schemes, like IMS 7.1's High Availability Large Database (HALDB), that overlay full function databases. However, DEDB performance benefits come at the expense of efficient space utilization; consequently, DEDBs require vigilant space monitoring because they do not dynamically extend their data sets. If a DEDB area data set should suffer space problems because the overflow or sequential dependent portions have been filled, then the business application will incur an expensive outage.

Resolving a full area condition has historically been a disruptive and protracted process. The conventional procedure of unloading and reloading all of the segment data can easily take more than an hour for even a modestly sized area. This document describes the techniques by which DEDB area data sets can be quickly and efficiently extended using a programmatic solution.


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