User-defined routines and header files

The database server calls a purpose function to initiate a specific task. Often, the purpose function calls other modules in the access-method library. For example, the scanning, insert, and update purpose functions might all call the same UDR to check for valid data type.

A complete access method provides modules that convert data formats, detect and recover from errors, commit and roll back transactions, and perform other tasks. You provide the additional UDRs and header files that complete the access method.