The federated server

The database server in a federated system is referred to as the federated server. Any number of database instances can be configured to function as federated servers. You can use existing database instances as your federated servers, or you can create new ones specifically for the federated system.

The database instance that manages the federated system is called a server because it responds to requests from end users and client applications. The federated server often sends parts of the requests it receives to the data sources for processing. A pushdown operation is an operation that is processed remotely. The database instance that manages the federated system is referred to as the federated server, even though it acts as a client when it pushes down requests to the data sources.

Like any other application server, the federated server is a database manager instance. Application processes connect and submit requests to the database within the federated server. However, two main features distinguish it from other application servers:

A federated server is configured to receive requests that might be partially or entirely intended for data sources. The federated server distributes these requests to the data sources.
Like other application servers, a federated server uses DRDA communication protocols (over TCP/IP) to communicate with database instances. However, unlike other application servers, a federated server uses the native client of the data source to access the data source. For example, a federated server uses the Sybase Open Client to access Sybase data sources and an Microsoft SQL Server ODBC Driver to access Microsoft SQL Server data sources.