Steps to creating and using a user-defined function

A user-defined function is similar to a host language subprogram or function. However, a user-defined function is often the better choice for an SQL application because you can invoke it in an SQL statement.

This section contains information that applies to all user-defined functions and specific information about user-defined functions in languages other than Java™.

Creating and using a user-defined function involves these steps:
  • Setting up the environment for user-defined functions
    A systems administrator probably performs this step. The user-defined function environment is shown in the following figure.
    Figure 1. The user-defined function environment
    Begin figure summary.A set of boxes show the flow between the program address space, DB2, and the WLM address space. Detailed description available.
    It contains an application address space, from which a program invokes a user-defined function; a Db2 system, where the packages from the user-defined function are run; and a WLM-established address space, where the user-defined function is executed. The steps for setting up and maintaining the user-defined function environment are the same as for setting up and maintaining the environment for stored procedures in WLM-established address spaces.
  • Writing and preparing the user-defined function

    This step is necessary only for an external user-defined function.

    The person who performs this step is called the user-defined function implementer.

  • Defining the user-defined function to Db2

    The person who performs this step is called the user-defined function definer.

  • Invoking the user-defined function from an SQL application

    The person who performs this step is called the user-defined function invoker.