For application programs that were written under Oracle Rdb V3.1 or
    earlier, use the two-phase commit protocol simply by recompiling
    your programs. You must use the /DISTRIBUTED_TRANSACTION
    qualifier in the precompiler command line. When you do this,
    Oracle Rdb invokes the DECdtm system service calls for your
    application. For example, to recompile the C program SAMPLE.RC
    with the RDML preprocessor, use the following command:

    $ RDML :== $RDML/C
    $ RDML
    SOURCE FILE> SAMPLE /DISTRIBUTED_TRANSACTION