IBM Information Server, Version 8.1Central components of a federated system include the federated server and the federated database.
In a federated system, the server that receives query requests and distributes those queries to remote data sources is referred to as the federated server. A federated server embeds an instance of DB2® to perform query optimization and to store statistics about remote data sources.
Application processes connect and submit requests to the database within the federated server. A federated server is configured to receive requests that might be intended for data sources. The federated server distributes these requests to the data sources.
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.
To users and client applications, data sources appear as a single relational database. Users and applications interface with the federated database that is managed by the federated server.
The federated database system catalog contains entries that identify data sources and their characteristics. The federated server consults the information that is stored in the federated database system catalog and the data source connector to determine the best plan for processing SQL statements.
The federated system processes SQL statements as if the data from the data sources were ordinary relational tables or views within the federated database.
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