UNIX System Services
| Company type | Software component |
|---|---|
| Industry | Computer software |
| Founder | IBM |
| Headquarters | United States |
| Products | UNIX operating system implementation (XPG4 UNIX 95) |
| Owner | IBM |
| Parent | z/OS |
z/OS UNIX System Services (commonly known as z/OS UNIX or USS) represents an essential element of z/OS, delivering a certified UNIX operating system implementation (specifically XPG4 UNIX 95) tailored for IBM mainframe hardware. Distinguished as the inaugural UNIX 95 platform not based on AT&T code, USS is tightly integrated with z/OS, extending the capabilities of Time Sharing Option (TSO) commands and enabling UNIX file manipulation through ISPF. Additionally, it incorporates extensions to JCL that facilitate batch processing of UNIX files.
Overview
UNIX System Services allows UNIX applications from different environments to operate on IBM System z mainframes running z/OS, frequently requiring nothing more than recompilation. Supporting both ASCII and Unicode character sets, z/OS UNIX also provides application-level conversion services for EBCDIC to meet mainframe requirements. Programs running under USS enjoy secure access to z/OS internal resources, including Db2 database connectivity via Call Attach; however, this level of integration reduces portability to other platforms. Adherence to POSIX and ANSI C standards enhances the ability to port applications across various UNIX systems.
The file systems available within z/OS UNIX consist of the legacy HFS and the preferred modern zFS, both supporting UNIX-style long filenames while appearing as datasets within z/OS. Several critical components of z/OS depend on USS, such as the z/OS Management Facility, XML services, OpenSSH, IBM HTTP Server for z/OS, the z/OS SDK for Java, and certain PKI functions. The OMVS shell environment is provided by USS.
Originating from OpenEdition MVS introduced in MVS/ESA SP 4.3 and further developed in version 5.1 with X/OPEN certification, USS has been consistently enhanced by IBM with every new release of z/OS.