UNIX System Services
Encyclopedia
UNIX System Services is a required, included component of z/OS
. USS is a certified UNIX
implementation (XPG4 UNIX 95) optimized for mainframe architecture. It is the first UNIX 95 to not be derived from the AT&T
source code. Through integration with the rest of z/OS, additional Time Sharing Option
(TSO) commands are available alongside the usual UNIX services, making it possible to process UNIX files using ISPF
. Extensions in JCL
make it possible to use these files in batch processing
.
UNIX System Services allows UNIX applications from other platforms to run on IBM mainframe
s. In many cases only a recompile is necessary, although additional effort may be advisable for z/OS
integration (such as SMP/E
installation support). Binary programs using hardcoded ASCII
numerical values may need adjustment — z/OS
users often prefer or require EBCDIC
support. Programs running under USS have full, secure access to the 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 standards such as POSIX and ANSI C
, it will be easier to port to the USS environment.
The file systems for USS (the older HFS
and the now preferred zFS
), which support UNIX-style long filename
s, appear as special dataset
s to the rest of z/OS
. Numerous core System z subsystems and applications rely on UNIX System Services, including Java
.
USS also provides a shell
environment, OMVS.
USS's predecessor was an operating system component called OpenEdition MVS, first implemented in MVS/ESA 4.3 and enhanced in MVS/ESA 5.1. OpenEdition MVS only supported the POSIX
standards. IBM continues to enhance UNIX System Services. In 2007, IBM announced z/OS 1.9 which includes several new USS features, including partial alignment with the newer Single UNIX Specification
Version 3 (UNIX 03).
Z/OS
z/OS is a 64-bit operating system for mainframe computers, produced by IBM. It derives from and is the successor to OS/390, which in turn followed a string of MVS versions.Starting with earliest:*OS/VS2 Release 2 through Release 3.8...
. USS is a certified UNIX
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
implementation (XPG4 UNIX 95) optimized for mainframe architecture. It is the first UNIX 95 to not be derived from the AT&T
AT&T
AT&T Inc. is an American multinational telecommunications corporation headquartered in Whitacre Tower, Dallas, Texas, United States. It is the largest provider of mobile telephony and fixed telephony in the United States, and is also a provider of broadband and subscription television services...
source code. Through integration with the rest of z/OS, additional Time Sharing Option
Time Sharing Option
In computing, Time Sharing Option is an interactive time-sharing environment for IBM mainframe operating systems, including OS/360 MVT, OS/VS2 , MVS, OS/390, and z/OS.- Overview :TSO fulfills a similar purpose to Unix login sessions...
(TSO) commands are available alongside the usual UNIX services, making it possible to process UNIX files using ISPF
ISPF
In computing, Interactive System Productivity Facility is a software product for the z/OS operating system that runs on IBM mainframes...
. Extensions in JCL
Job Control Language
Job Control Language is a scripting language used on IBM mainframe operating systems to instruct the system on how to run a batch job or start a subsystem....
make it possible to use these files in batch processing
Batch processing
Batch processing is execution of a series of programs on a computer without manual intervention.Batch jobs are set up so they can be run to completion without manual intervention, so all input data is preselected through scripts or command-line parameters...
.
UNIX System Services allows UNIX applications from other platforms to run on IBM mainframe
IBM mainframe
IBM mainframes are large computer systems produced by IBM from 1952 to the present. During the 1960s and 1970s, the term mainframe computer was almost synonymous with IBM products due to their marketshare...
s. In many cases only a recompile is necessary, although additional effort may be advisable for z/OS
Z/OS
z/OS is a 64-bit operating system for mainframe computers, produced by IBM. It derives from and is the successor to OS/390, which in turn followed a string of MVS versions.Starting with earliest:*OS/VS2 Release 2 through Release 3.8...
integration (such as SMP/E
SMP/E
SMP/E is a standard utility used in conjunction with IBM's z/OS operating system. SMP/E is the common installation tool for managing operating system components and middleware on z/OS...
installation support). Binary programs using hardcoded ASCII
ASCII
The American Standard Code for Information Interchange is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text...
numerical values may need adjustment — z/OS
Z/OS
z/OS is a 64-bit operating system for mainframe computers, produced by IBM. It derives from and is the successor to OS/390, which in turn followed a string of MVS versions.Starting with earliest:*OS/VS2 Release 2 through Release 3.8...
users often prefer or require EBCDIC
EBCDIC
Extended Binary Coded Decimal Interchange Code is an 8-bit character encoding used mainly on IBM mainframe and IBM midrange computer operating systems....
support. Programs running under USS have full, secure access to the internal functions of z/OS. Database access (DB2
IBM DB2
The IBM DB2 Enterprise Server Edition is a relational model database server developed by IBM. It primarily runs on Unix , Linux, IBM i , z/OS and Windows servers. DB2 also powers the different IBM InfoSphere Warehouse editions...
via Call Attach) is one example of how USS can access services found elsewhere in z/OS
Z/OS
z/OS is a 64-bit operating system for mainframe computers, produced by IBM. It derives from and is the successor to OS/390, which in turn followed a string of MVS versions.Starting with earliest:*OS/VS2 Release 2 through Release 3.8...
. 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 standards such as POSIX and ANSI C
ANSI C
ANSI C refers to the family of successive standards published by the American National Standards Institute for the C programming language. Software developers writing in C are encouraged to conform to the standards, as doing so aids portability between compilers.-History and outlook:The first...
, it will be easier to port to the USS environment.
The file systems for USS (the older HFS
HFS
HFS may stand for:* Hyperfine structure* Hereditarily finite set* Hexafluorosilicic acid* WHFS , 'HFS was a slang abbreviation for the radio stations with that call sign in the Washington / Baltimore area...
and the now preferred zFS
ZFS (IBM file system)
zFS refers to two different IBM file systems:* zFS most often refers to z/OS Distributed File Service zSeries File System, the newest POSIX-style hierarchical file system for IBM's z/OS operating system, a successor to that operating system's HFS...
), which support UNIX-style long filename
Long filename
Long filenames , are Microsoft's way of implementing filenames longer than the 8.3 filename, or short-filename, naming scheme used in Microsoft DOS in their modern FAT and NTFS filesystems. Because these filenames can be longer than an 8.3 filename, they can be more descriptive...
s, appear as special dataset
Data set (IBM mainframe)
data set , dataset , is a computer file having a record organization. The term pertains to the IBM mainframe operating system line, starting with OS/360, and is still used by its successors, including the current z/OS. Those systems historically preferred this term over a file...
s to the rest of z/OS
Z/OS
z/OS is a 64-bit operating system for mainframe computers, produced by IBM. It derives from and is the successor to OS/390, which in turn followed a string of MVS versions.Starting with earliest:*OS/VS2 Release 2 through Release 3.8...
. Numerous core System z subsystems and applications rely on UNIX System Services, including Java
Java (programming language)
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
.
USS also provides a shell
Shell (computing)
A shell is a piece of software that provides an interface for users of an operating system which provides access to the services of a kernel. However, the term is also applied very loosely to applications and may include any software that is "built around" a particular component, such as web...
environment, OMVS.
USS's predecessor was an operating system component called OpenEdition MVS, first implemented in MVS/ESA 4.3 and enhanced in MVS/ESA 5.1. OpenEdition MVS only supported the POSIX
POSIX
POSIX , an acronym for "Portable Operating System Interface", is a family of standards specified by the IEEE for maintaining compatibility between operating systems...
standards. IBM continues to enhance UNIX System Services. In 2007, IBM announced z/OS 1.9 which includes several new USS features, including partial alignment with the newer Single UNIX Specification
Single UNIX Specification
The Single UNIX Specification is the collective name of a family of standards for computer operating systems to qualify for the name "Unix"...
Version 3 (UNIX 03).