|
Unix System Services (USS) is a component of z/OS. USS is an adequate, certified Unix implementation (XPG4 UNIX 95). It is the first Unix 95 which was not derived from the AT&T/SCO source code. By the integration in z/OS, additional time share option (TSO) commands are available next to the usual Unix services, making it possible to process Unix files by using ISPF. Extensions in the JCL make it possible to use these files in batch processings.
Unix System Services allows Unix applications to be run on mainframes by IBM, implementing Unix-based services on these computers. Binary programs using the numerical values of ASCII remain the only form of incompatibility — the zSeries architecture is based on EBCDIC. Programs running under USS have full access to the internal functions of z/OS. If this feature is used at all, it is mainly employed in database access (DB2 via Call Attach). Naturally these programs cannot be ported without rewriting, should they use these internal mechanisms.
The file systems of the USS (HFS or ZFS) appears as special datasets to the rest of the z/OS.
Predecessor of the Unix System Services was an operating system component called Open MVS, which was first implentend in MVS/ESA 4.3. It only supported the POSIX standards.
|
