What is USS?

[Anuj Dhawan]

The UNIX® System Services element of z/OS® is tightly integrated into the operating system. You get the best of both worlds: UNIX and z/OS. UNIX System Services is a key element of our open and distributed computing strategy.

Many critical z/OS functions and services depend on UNIX System Services and would never be able to function otherwise, including the z/OS Management Facility, XML parsing and generation services, OpenSSH, the IBM HTTP Server for z/OS, the z/OS SDK for Java, and some z/OS PKI services as examples.

UNIX System Services allows UNIX applications from other platforms to run on IBM System z mainframes running z/OS. In many cases only a recompile is necessary, although additional effort may be advisable for z/OS integration (such as SMP/E installation support). While USS supports ASCII and Unicode, and there's no technical requirement to modify ASCII and Unicode UNIX applications, many z/OS users often prefer EBCDIC support in their applications including those running in USS. Consequently USS provides application and administrator services for converting to/from EBCDIC. Programs running under USS have full, secure access to the other internal functions of z/OS. Database access (DB2 via Call Attach) is one example of how USS can access services found elsewhere in z/OS. Naturally such programs cannot be ported to non-mainframe platforms without rewriting if they use these z/OS-specific services. Conversely, if a program adheres to UNIX® standards such as POSIX and ANSI C, it will be easier to move them between different UNIX® operating systems including z/OS UNIX®.

Here is good explanation by IBM: http://www-03.ibm.com/systems/z/os/zos/features/unix/" onclick="window.open(this.href);return false;