Mainframes

MAINFRAMES

AS/400

(Application System/400) The earlier generation and original name of IBM's iSeries and i5 families of midrange business computers. Introduced in 1988, the AS/400 evolved into the iSeries in 2000 and the i5 in 2004. When first introduced, the AS/400 was considered a "minicomputer."

OS/390

The primary operating system used in IBM mainframes. OS/390 was originally the MVS/ESA operating system renamed and repackaged in 1996 with an extensive set of utilities. Although the name MVS is still used to refer to the base control program of OS/390, enhancements in usability and workload balancing have made OS/390 stand apart from its MVS heritage. OS/390 is upward compatible from MVS/ESA 5.2.2, but downward compatibility is not ensured.

z/OS

A mission critical mainframe operating system that extends OS/390 to IBM's zSeries eServers. Although in its first release there are few functional enhancements compared to OS/390 Version 2 Release 10, many more are expected. z/OS, Version 1 Release 1 runs on G5 and G6 Parallel Enterprise Servers, Multiprise 3000 Servers and supports 64-bit real memory addressing on the z900 (64-bit virtual storage is expected). On the G5 and G6, z/OS uses 31-bit addressing and is somewhat restricted. When IBM introduced its zSeries 800 in 2002 for the mid-size market, it introduced a lower-priced version of z/OS known as "z/OS.e."

OS/400

The operating system for the iSeries family of midrange computers from IBM. Introduced in 1988 for the AS/400 (renamed iSeries in 2000), the OS/400 communicates with the hardware through the Licensed Internal Code (LIC) layer, which includes the device drivers. In 2004, OS/400 was renamed i5/OS to coincide with the eServer i5 models introduced in that same year

VAX

(Virtual Address eXtension) A venerable family of 32-bit computers from HP (via Digital and Compaq) introduced in 1977 with the VAX-11/780. VAX models ranged from desktop units to mainframes all running the same VMS operating system, and VAXes could emulate PDP models (Digital's first computers). Large VAX multiprocessing clusters served thousands of users.

COBOL

(COmmon Business Oriented Language) A high-level programming language that has been the primary business application language on mainframes and minis. It is a compiled language and was one of the first high-level languages developed. Officially adopted in 1960, COBOL stemmed from FLOWMATIC, a language developed in the mid-1950s by Grace Murray Hopper (later Rear Admiral Hopper) for the UNIVAC I.

COBOL is a very wordy language. Although mathematical expressions can also be written like other programming languages (see example below), its verbose mode is very readable for a novice. For example, multiply hourly-rate by hours-worked giving gross-pay is self-explanatory

CICS

(Customer Information Control System) A TP monitor from IBM that was originally developed to provide transaction processing for IBM mainframes. It controls the interaction between applications and users and lets programmers develop screen displays without detailed knowledge of the terminals used. It provides terminal routing, password security, transaction logging for error recovery and activity journals for performance analysis.

CICS has also been made available on non-mainframe platforms including the RS/6000, AS/400 and OS/2-based PCs.

CICS commands are written along with and into the source code of the applications, typically COBOL, although assembly language, PL/I and RPG are also used. CICS implements SNA layers 4, 5 and 6.

MVS

(Multiple Virtual Storage) Introduced in 1974, the primary operating system used with IBM mainframes (the others are VM and DOS/VSE). MVS is a batch processing-oriented operating system that manages large amounts of memory and disk space. Online operations are provided with CICS, TSO and other system software.

DB2

(DATABASE 2) A relational DBMS from IBM that was originally developed for its mainframes. It is a full-featured SQL language DBMS that has become IBM's major database product. Known for its industrial strength reliability, IBM has made DB/2 available for all of its own platforms, including OS/2, OS/400, AIX (RS/6000) and OS/390, as well as for Solaris on Sun systems and HP-UX on HP 9000 workstations and servers

IDMSX

(Integrated Data Management System EXtended) A database management system (DBMS) from Fujitsu Services, formerly ICL, that is widely used on its VME mainframes. It supports journaling, recovery and locking options. A single IDMSX database can contain up to a terabyte of data

IMS

Information Management System) An early IBM hierarchical DBMS for IBM mainframes. IMS was widely implemented throughout the 1970s under MVS and continues to be used under z/OS. IMS/DB (IMS/DataBase) is the back end database part, and either IMS/TM (IMS/Transaction Manager) or CICS provides the front end online interaction.

IMS/TM, formerly IMS/DC (IMS/Data Communications), runs each transaction in its own address space and allows for more precise tuning than CICS, which runs all transactions in a region. IMS/TM is also used to access DB2 databases, and Java applications can access IMS databases

TANDEM

(Tandem Computers Inc., Cupertino, CA) A former major manufacturer of fault-tolerant computers founded in 1974 by James Treybig and provider of the early 21st century technology for HP's enterprise computing strategy. Tandem was the first company to address the transaction processing (OLTP) market for online reservations and financial transfers by providing computers designed from the ground up for fault-tolerant operation. These computers are used in all the major banks, stock exchanges, credit card companies and ATM machines in the world.

Tandem's most significant product was its MIPS-based Himalaya series which ran the NonStop Kernel operating system, compatible with Tandem's Guardian OS. This platform lives on in the NonStop S-series servers from HP, which acquired Tandem's technology via Compaq in 2002. Compaq had purchased Tandem in 1997

Xpeditor

A family of mainframe testing programs from Compuware. It provides the programmer with an assortment of debugging tools for TSO, IMS and other mainframe applications

RPG

Report Program Generator) One of the first program generators designed for business reports, introduced in 1964 by IBM. In 1970, RPG II added enhancements that made it a mainstay programming language for business applications on IBM's System/3x midrange computers. RPG III and RPG IV added more enhancements and have been widely used on the AS/400. RPGLE added the "Integrated Language Environment (ILE)," which enables C, Java and other modules to be integrated into the program.

Until RPGLE, all processing statements were written in strict columnar format. The following RPGLE example changes Fahrenheit to Celsius. The A lines are Data Description Specs (DDS) code. They define a display file and are compiled separately