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The SCO UnixWare 2.1.X compatibility module works by installing UnixWare 7 versions of the shared libraries loaded by an application on SCO UnixWare 2.1.X, as well as installing the UDK tools.
The BCM for SCO UnixWare 2.1.X works differently than the BCM for SCO OpenServer (see ``How the BCM works on SCO OpenServer''). Rather than providing UnixWare 7 libraries in an alternate udk directory tree, the SCO UnixWare 2.1.X BCM replaces existing libraries with UnixWare 7 libraries. Consequently, there is no need for the elfmark(1) command on SCO UnixWare 2.1.X systems.
After installing the SCO UnixWare 2.1.X BCM, all binaries are executed with the updated set of libraries, effectively extending the SCO UnixWare 2.1.X APIs to provide UnixWare 7 interfaces.
An example is the UnixWare 7 libc for SCO UnixWare 2.1.X, which maps data structures and constants that are different on the two platforms. There is no need to map system calls numbers and error returns, since the UnixWare 7 and SCO UnixWare 2.1.X implementations of these interfaces are similar.