To Create User Exits

1. In C code, create either a shared object (UNIX systems) or a DLL (Windows) and create or export a routine to be called from Extract or Replicat. This routine is the communication point between Oracle GoldenGate and your routines. Name the routine whatever you want. The routine must accept the following Oracle GoldenGate user exit parameters:

   • EXIT_CALL_TYPE: Indicates when, during processing, the routine is called.

   • EXIT_CALL_RESULT: Provides a response to the routine.

   • EXIT_PARAMS: Supplies information to the routine. This function enables you to use the EXITPARAM option of the TABLE or MAP statement to pass a parameter that is a literal string to the user exit. This is only valid during the exit call to process a specific record. This function also enables you to pass parameters specified with the PARAMS option of the CUSEREXIT parameter at the exit call startup.

2. In the source code, include the usrdecs.h file. The usrdecs.h file is the include file for the user exit API. It contains type definitions, return status values, callback function codes, and a number of other definitions. The usrdecs.h file is installed within the Oracle GoldenGate directory. Do not modify this file.

3. Include Oracle GoldenGate callback routines in the user exit when applicable. Callback routines retrieve record and application context information, and they modify the contents of data records. To implement a callback routine, use the ERCALLBACK function in the shared object. The user callback routine behaves differently based on the function code that is passed to the callback routine.

   ERCALLBACK (function_code, buffer, result_code);
   

   Where:

   • function_code is the function to be executed by the callback routine.

   • buffer is a void pointer to a buffer containing a predefined structure associated with the specified function code.

   • result_code is the status of the function that is executed by the callback routine. The result code that is returned by the callback routine indicates whether or not the callback function was successful.

   • On Windows systems, Extract and Replicat export the ERCALLBACK function that is to be called from the user exit routine. The user exit must explicitly load the callback function at run-time using the appropriate Windows API calls.

4. Include the CUSEREXIT parameter in your Extract or Replicat parameter file. This parameter accepts the name of the shared object or DLL and the name of the exported routine that is to be called from Extract or Replicat. You can specify the full path of the shared object or DLL or let the operating system's standard search strategy locate the shared object.

   CUSEREXIT {DLL | shared_object} routine
   [, INCLUDEUPDATEBEFORES]
   [, PARAMS 'startup_string']
   

   Where:

   • DLL is a Windows DLL and shared_object is a UNIX shared object that contains the user exit function.

   • INCLUDEUPDATEBEFORES gets before images for UPDATE operations.

   • PARAMS 'startup_string' supplies a startup string, such as a startup parameter.