Mapping functions and user-defined functions

Function mappings associate federated server functions and user-defined functions with the existing functions at the data source.

Function mappings in a federated system
Federation component supplies default mappings between existing data source functions and database counterpart functions.
User-defined functions in applications
Application developers often need to create their own suite of functions specific to their application or domain. They can use user-defined scalar functions for this purpose.
Creating function mappings
Use the CREATE FUNCTION MAPPING statement to specify alternative function mappings that override the default function mappings.
Function templates
The federated server recognizes a data source function when there is a mapping between the data source function and a database counterpart function at the federated database.
Disabling a default function mapping
Default function mappings cannot be dropped. However, you can render them inoperable by disabling them.
Dropping a function mapping
When you no longer require a function mapping that you created, you can delete the function mapping by running the DROP statement.

Parent topic: Administering federation

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