Distributed relational database function and SQL
A distributed relational database consists of a set of SQL objects that are spread across interconnected computer systems.
These relational databases can be of the same type (for example, the DB2® for i database) or of different types (DB2 for z/OS®, DB2 for VSE and VM, or non-IBM database management systems that support Distributed Relational Database Architecture™ (DRDA)). Each relational database has a relational database manager to manage the tables in its environment. The database managers communicate and cooperate with each other in a way that allows a given database manager access to run SQL statements on a relational database on another system.
The application requester supports the application side of a connection. The application server is the local or remote database to which an application requester is connected. DB2 for i provides support for DRDA to allow an application requester to communicate with application servers. In addition, DB2 for i can call exit programs to allow access to data on other database management systems that do not support DRDA. These exit programs are called application requester driver (ARD) programs.
- Remote unit of work (RUW)
A remote unit of work is where the preparation and running of SQL statements occurs at only one application server during a unit of work. DB2 for i supports RUW over either Advanced Program-to-Program Communication (APPC) or TCP/IP.
- Distributed unit of work (DUW)
A distributed unit of work is where the preparation and running of SQL statements can occur at multiple application servers during a unit of work. However, a single SQL statement can only refer to objects located at a single application server. DB2 for i supports DUW over APPC and DUW over TCP/IP.