Distributed data facility
The distributed data facility (DDF) allows client applications that run in an environment that supports DRDA to access data at Db2 servers. In addition, a Db2 application can access data at other Db2 servers and at remote relational database systems that support DRDA.
DDF supports TCP/IP and Systems Network Architecture (SNA) network protocols. DDF allows the Db2 server to act as a gateway for remote clients and servers. A Db2 server can forward requests on behalf of remote clients to other remote servers regardless of whether the requested data is on the Db2 server.
With DDF, you can have up to 150,000 connections to a single Db2 server at the same time. You can only have up to 2000 threads running concurrently. A thread is a Db2 structure that describes an application's connection and traces its progress.
DDF uses methods for transmitting query result tables that minimize network traffic when you access distributed data. You can also use stored procedures to reduce processor and elapsed-time costs of distributed access. A stored procedure is user-written SQL program that a requester can invoke at the server. When you encapsulate SQL statements to the Db2 server into a single message, many fewer messages flow across the wire.
Local Db2 applications can also use stored procedures to take advantage of the ability to encapsulate SQL statements that are shared among different applications.
In addition to optimizing message traffic, DDF enables you to transmit large amounts of data efficiently by using the full bandwidth of the network.
DDF also enables applications that run in a remote environment that supports DRDA. These applications can use DDF to access data in Db2 servers. Examples of application requesters include IBM® DB2 Connect and other DRDA-compliant client products.
The decision to access distributed data has implications for many Db2 activities: application programming, data recovery, and authorization, to name a few.