IBM moving DRDA forward - Distributed Relational Database Architecture

Software Magazine, Nov, 1991 by Barbara Bochenski

While IBM supports and participates in the industry's efforts toward Remote Data Access (RDA), Big Blue is forging ahead with its own Distributed Relational Database Architecture (DRDA). DRDA is IBM's architecture for enabling customers to access distributed data across all four of its Systems Applications Architecture (SAA) relational database systems.

The remote-unit-of-work (RUOW) distributed database capability, based on DRDA, permits users to access relational data residing on DB2, SQL/DS and OS/400 databases. It also enables OS/2 database manager connectivity to these host database systems as a RUOW client.

Target availability dates, according to IBM, are as follows: DB2 in March 1992, OS/400 in March 1992, and SQL/DS in May 1992. IBM said it would deliver distributed capability for OS/2 as a RUOW client when the distributed support for the host operating system is available. So in March 1992, an OS/2 workstation should be able to access distributed data as a RUOW client from either DB2 or an OS/400 database.

George Zagelow, manager of architecture and standards for IBM's Santa Teresa Labs in San Jose, Calif., said IBM has been involved in development of the RDA standard in the International Organization for Standardization (ISO) since 1986. He said IBM has pushed hard to permit progress to be made with the standard.

"We have a large customer base which is insisting that we deliver distributed database with certain characteristics," said Zagelow. He said IBM has tried to expand RDA to meet customer requirements.

"We have no choice but to go forward," he added. "We can't not do what our customer ask for. Industry will support RDA in the future, and we will, too."

He said the bottom line is that the customers win because they will have expanded capabilities with DRDA now, yet IBM will support the RDA standard in the future. "RDA will be easier to implement," said Zagelow, "but DRDA provides management and operational considerations like systems management, job accounting and performance capabilities that RDA does not provide."

Critics point out that in DRDA's design, a client application must use the variant of SQL supported by the data manager at a particular server. There are differences in the SQL supported by DB2, SQL/DS, OS/400 and 0S/2 Extended Edition.

IBM's SAA SQL provides a definition of SQL that will work across all SAA-compliant data managers. However, critics say that while this helps pull together the SQL variants supported by the four IBM SAA data managers, there are areas in data type support and privileges where data managers specifics still show through.

Critics say that this SAA definition is primarily based on existing IBM SQL variants, and that it is not a multivendor specification like an international standard.