The sql_register_error_handler routine registers the
    application's error handling routine with SQL. When SQL
    determines that it will return a negative value for SQLCODE, SQL
    calls the error handling routine that is currently registered.
    The standard error handling routines are always in effect,
    whether special error handling routines have been registered or
    not. After the error handling routine executes, control returns
    to SQL.

    An application can contain and call more than one error handling
    routine. However, only one routine can be active at a time.

    An application can use the sql_get_error_handler routine to store
    the address of a registered routine for use later in the program.

    To deregister a routine, use the sql_deregister_error_handler
    routine.

    For information about declaring the error handling routines in
    the supported programming languages, see the Oracle Rdb Guide to
    SQL Programming.