What Is DRDA?

DRDA is a set of protocols, or rules, that enable a user to access distributed data regardless of where it physically resides. It provides an open , robust heterogeneous distributed database environment. DRDA provides methods of coordinating communication among distributed locations. This allows applications to access multiple remote tables at various locations and have them appear to the end user as if they were a logical whole.

A distinction should be made, however, between the architecture and the implementation. DRDA describes the architecture for distributed data and nothing more. It defines the rules for accessing the distributed data, but it does not provide the actual application programming interfaces (APIs) to perform the access. So DRDA is not an actual program, but is more like the specifications for a program.

When a DBMS is said to be DRDA-compliant, all that is implied is that it follows the DRDA specifications. DB2 is a DRDA-compliant RDBMS product.

Benefits of DRDA

DRDA is only one protocol for supporting distributed RDBMS. Of course, if you are a DB2 user, it is probably the only one that matters.

The biggest benefit provided by DRDA is its clearly stated set of rules for supporting distributed data access. Any product that follows these rules can seamlessly integrate with any other DRDA-compliant product. Furthermore, DRDA-compliant RDBMSs support full data distribution including multi-site update. The biggest advantage, however, is that it is available today, and many vendors are jumping on the DRDA-compliance bandwagon.

An alternative to DRDA is to use a gateway product to access distributed data. Gateways are comprised of at least two components : one for each distributed location. These parts communicate with one another. As far as DB2 is concerned , a host-based gateway component is necessary. It functions as another mainframe DB2 application. Most gateway products that access DB2 execute using CICS or VTAM. Gateways, however, typically support dynamic SQL only.

Therefore, two more advantages of DRDA surface in the performance arena:

• The removal of the overhead associated with the gateway and its code

• The removal of reliance upon and the inevitable performance degradation associated with it

What About RDA?

Although DRDA is the distributed architecture utilized by DB2, it is not the only architecture in the industry. RDA (Remote Database Access) is a competing set of protocols developed by the ISO and ANSI standard committees .

As a DB2 developer, DRDA will be the method you use to implement distributed data with DB2. However, knowing a bit about RDA cannot hurt.

• RDA was built to work with a standard subset of SQL that is available from DBMS to DBMS. DRDA was built to function with platform-specific extensions to SQL.

• Static SQL can be used with DRDA; with RDA only dynamic SQL is available.