IBM's DRDA paves way to interoperability; but work remains for IBM, third parties to achieve cross-platform RDBMS access - IBM's Distributed Relational Database Architecture client/server architecture for accessing remote relational data

Software Magazine, Nov, 1993 by Barbara Francett

DRDA is IBM's client/server architecture for accessing remote relational data across IBM and non-IBM platforms. Though RDBMS vendor support and customer demand for DRDA have been slow, 'interest is mounting. IBM is working to enhance DRDA with support for more non-IBM platforms and protocols, as well as for management tools. Mobil Natural Gas cites platform flexibility as the chief benefit to DRDA.

But work remains for IBM, third parties to achieve cross-platform RDBMS access

Distributed Relational Database Architecture (DRDA) is IBM's client/server architecture for accessing remote relational data across IBM and non-IBM platforms. For users to realize DRDA's interoperability goals, however, more work remains to be done by both IBM and relational database management system (RDBMS) vendors.

DRDA is a published set of protocols that permits multiple database systems to work together. The protocols define what needs to be exchanged to coordinate communication between relational database systems, and how to accomplish those exchanges. Software vendors can license DRDA technology to develop DRDA-conformant products that will be able to exchange data between heterogeneous applications and RDBMSs.

Initial vendor and customer interest in DRDA has been slow to develop. However, several RDBMS vendors report that their customers -- particularly their mainframe customers -- are becoming increasingly interested in DRDA to broaden their access to IBM databases from lowercost platforms. This interest has spurred these vendors to license the technology and to begin adding DRDA support to their products. Ultimately, the success of DRDA will hinge on how widely other vendors not just IBM implement it in their products.

Conceptually, DRDA dates back to the mid-80s, said George Zagelow, manager of architecture and standards, software solutions division at IBM's Santa Teresa Laboratories, San Jose, Calif. At that time, IBM sot into motion a three-part relational strategy: to take relational database technology. across all its strategic environments, with a standardized Structured Query Language (SQL) as the application programming interface (API); to build a "best-of-breed" relational database in all environments; and to develop interoperability across those em4ronments.

* The second part of the strategy resulted in the expansion of the DB2 family; the third part resulted in DRDA. DRDA uses SQL as its single common interface, supporting all of SQL's many dialects. Thus, it fulfills the first part of the strategy's intent. As the effort proceeded, however, it became obvious that a clash between central IS and user groups was developing in many firms. Central IS wanted to maintain strict controls over information assets in corporate mainframes, while user groups were eager to utilize desktop workstation technologies. "When we put DRDA together, our mindset was how to integrate those two communities," said Zagelow.

As a result, DRDA became IBM's approach not only to distributed databases in general, but to client/server technology in particular. Moreover, Zagelow said, based on customer input. it became clear that IBM needed to broaden the project's initial scope to include other vendors. IBM decided that it would open up the specification to other vendors once it was written and tested.

IBM published the first DRDA specification in August 1990. Over the following months, IBM products supporting DRDA followed. Today, they include DB2 (for MVS), SQL/DS (for VM and VSE/ESA), OS/400 (for the AS/400), DB2/6000 (for the RS/6000) and DB2/2 (for OS/2). DB2/6000 and DB2/2 use IBM's Distributed Database Connection Services (DDCS) to connect to hosts.

IBM also established a developers' council, inviting a number of vendors to participate. Some of the participants include Borland International, Inc., Scotts Valley, Calif.; Cincom Systems, Inc., Cincinnati; Information Builders, Inc., New York City; Informix Software, Inc., Menlo Park, Calif.; The Ask Group, Mountain View, Calif.; Micro Decisionware, Boulder, Colo.; Novell, Inc., Provo, Utah; Object Technology International, Inc., Ottawa; Oracle Corp., Redwood Shores, Calif.; Progress Software Corp., Bedford, Mass.; Sybase, Inc., Emeryville, Calif; and XDB System, Inc., Laurel, Md. These developers could work with IBM and get advance information about extensions to the spec, or share any of their own extensions. However, products from other vendors have been slower to follow, and have only recently begun to appear.

LEARNING THE TERMINOLOGY

Acquiring even a working knowledge of DRDA requires learning some IBM-specific terminology. In DRDA, clients -- the computers requesting data for their applications -- are called application requesters. Servers -- the computers providing the data -- are called application servers.

DB2 for MVS is a DRDA client and a DRDA server. SQL/DS is a DRDA client and server on VM, and a DRDA server on VSE/ESA. SQL/400 is a DRDA client and server, DB2/6000 is a DRDA client, and DB2/2 is a DRDA client on AS/400, RS/6000, and OS/2 platforms. (See figure, p. 69.)