Server options that affect federated databases

A federated database system is composed of a Db2® data server (the federated database) and one or more data sources. You identify the data sources to the federated database when you issue CREATE SERVER statements. You can also specify server options that refine and control various aspects of federated system operation.

You must install the distributed join installation option and set the federated database manager configuration parameter to YES before you can create servers and specify server options. To change server options later, use the ALTER SERVER statement.

The server option values that you specify on the CREATE SERVER statement affect query pushdown analysis, global optimization, and other aspects of federated database operations. For example, you can specify performance statistics as server option values. The cpu_ratio option specifies the relative speeds of the processors at the data source and the federated server, and the io_ratio option specifies the relative rates of the data I/O divides at the data source and the federated server.

Server option values are written to the system catalog (SYSCAT.SERVEROPTIONS), and the optimizer uses this information when it develops access plans for the data source. If a statistic changes (for example, when a data source processor is upgraded), use the ALTER SERVER statement to update the catalog with the new value.