Support | Mainframe Dictionary | H
A glossary of terms important to IBM mainframe machines
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HA: High Availability. See High Availability Services.
Hacker: Anyone purposely attempting unauthorized access to a computer system, without the organization’s permission. See also firewall1.
HACL: IBM’s Host Access Class Library. Object-oriented, JavaAPI implemented on Host On-Demand that is now also available as an API on other Web-to-host products, e.g., Hummingbird’s HostExplorer Web.
HACMP: High Availability Cluster Multi-Processing software for the pSeries, announced June 1992. Designed to allow up to 32 pSeries systems to share critical components to provide high availability without too much redundant hardware. Different modes of coupling are possible: Mode 1 where one machine sits idle and takes over if another machine dies; Mode 2 where processors support their own users and applications, and provide mutual backup; and Mode 3 (loosely coupled multi-processing) where the machines support the same users and cooperatively run both applications. Mid 1995 it became HACMP for AIX.
HAGEO/GeoRM: High-Availability Geographic Cluster for AIX and Geographic Remote Mirror for AIX programs. Allows geographically dispersed sites to mirror customer data in real time using LAN or point-to-point networks. Basically a wide area version of the HACMP clustering technology.
HALDB: High Availability Large Databases. Enables partitioning of IMS DB databases, supporting as many as 1,001 partitions. Each partition can be 40GB. Partitions can be processed in parallel. ISPF panels with help screens are provided for creating and migrating databases. cf. Partition2. Announced as part of IMS1 Version 7 in August 1999.
Half duplex: Data communication terminology for the transmission of data in only one direction at a time. See Duplex.
HANDY: IBM expert system and artificial intelligence research project. Defunct.
Hardcoded: The use of a constant, rather than a variable, for a value in the source code of software. If there is ever a need to change that value, it is difficult and error-prone, especially if the value is used in more than one place in a program.
Hardware Management Console: See HMC.
Hardware monitor: A component of Tivoli NetView for z/OS that helps identify and solve problems related to physical network elements.
Hashing algorithm: A method used to transform a record’s key into a location within a file where the record will be stored.
HASP: Houston Automatic Spooling Program. Early batch job manager developed by IBM for in-house use and subsequently released as JES2 (which is why JES2 messages are always prefaced by HASP).
HA Switchable Resources: High Availability Switchable Resources. A chargeable OS/400 option that allows resources, typically disk drives, to be physically switched between systems, such as would be required should a production disk drive fail.
HCD: Hardware Configuration Definition. An element of z/OS that provides the interactive tool which is used to define the hardware configuration. HCD eliminates batch I/O gens. See also HCM.
HCF: Host Command Facility. Originally part of 8100 Host Support Services providing central control and operation of multiple 8100/DPPX systems, and distributed system management using NCCF facilities. Later a VTAM facility which allows one device to log on to another as if it is a local user, when it’s very useful for management of remote IBM and non-IBM devices. Withdrawn March 2001.
HCM: Hardware Configuration Manager. An optional, separately priced feature of z/OS that provides a client/server application for driving HCD. Announced June 1995.
HCPSADMP: Stand-Alone Dump Utility.
HDA: Head/Disk Assembly. The read/write head and associated bits and pieces that read data from disks. The implication is also of a sealed unit, at least from the customer perspective, as opposed to a removable disk pack.HDA
HDAM: Hierarchical Direct Access Method for IMS DB.
HDBV: Host DataBase View. Micro to mainframe link from IBM for business professionals. Allows access from PCs to certain tools, including QMF, AS, Info Center/1. Also re-formats data from some PC packages (e.g., Lotus1-2-3). Obsolete.
HDDI: Host Displaywriter Document Interchange. A venerable program which enabled Displaywriter users to transfer documents to a host machine. Defunct.
HDL: Host Document Library. The DISOSS library. Obsolete.
HDLC: High-level Data Link Control. A set of ISO standard link protocols for carrying data over a link with error and flow control. One variant is used by X.25, another is compatible with SDLC1.
Head of string: DASDsub control unit between a DASD controller and storage devices.
Heartbeat: Message passed between two processors in a fault-tolerant (e.g., XRF) configuration. The heartbeat tells the other processor that its colleague is alive and well.
Heavy metal: Obscure industryspeak for Big iron.
Helical scan: A technique for recording data onto magnetic tape where the data is stored in a series of diagonal stripes on the tape. Basically it’s a derivative of VCR technology but highly modified for data recording devices to reduce tape wear, improve reliability, etc. The technique was originally planned for use in the Magstar, but IBM engineers could not figure out how to avoid having to replace the tape head every month, so it was scrapped for good old fashioned parallel tracks which run along the length of the tape. The technique has long been used in the mid-range and PC markets (e.g., in the IBM 7208), but only started to come into the mainframe market with StorageTek’s Redwood device.
Help Desk: A facility, common in many IBM installations, which provides a single focal point for support services for end-users. At the end of 1989, IBM announced that it was providing such a service itself through its End-User Support program. In an alliance with Peregrine Systems, IBM formed an Infrastructure Resource Management (IRM) practice in August 2001 to provide, among other things, a Help Desk service offering.
HelpWare: PC service offering introduced by IBM early 1992 in the USA and the UK. You pay your money and you get a helpline, trade-in program, and a magazine. Aimed mainly at the stand-alone and small business user, not the corporates. One of IBM’s early attempts to differentiate itself from the clone vendors (and to avoid the hurly-burly of a commodity market) by offering service, rather than low prices. Still being offered for products such as the NetVista line.
Hercules: An obsolete screen standard for IBM PCs. Monochrome only, but fairly high resolution.
HESC: Higher Education Software Consortium. IBM discount scheme for US schools and colleges. Members pay a fixed membership fee and no software license fees. The program was terminated June 30, 2000.
HFGD: High Function Graphic Device (e.g., the 5080).
HFS: Hierarchical File System of z/OS Unix System Services and Unix-based operating systems such as AIX1.
HIDAM: Hierarchical Indexed Direct Access Method. Access method used in IMS DB.
High-Availability Cluster Multi-Processing: See HACMP.
High-Availability Geographic Mirror: See HAGEO/GeoRM.
High Availability Services: IBM fee-based offerings to assess, implement and support measures to increase the reliability of eservers.
High Level Assembler: Version of Assembler introduced early 1993 for z/OS, z/VM and VSE/ESA. Replaces Assembler H. An element of z/OS. aka HLASM. The HLASM Toolkit is an optional, separately priced feature of z/OS.
High Performance Optical File System: A replacement for FAT-based file systems within optical library hardware such as the 3995. It includes redundant control structures that help prevent data loss during unscheduled power outages. HPOFS also erases rewritable media in the background to boost data write performance by 33%.
HighPoint: Code name in the October 1993 Statement of Direction (SoD) for what became VisualGen, officially announced May 1994. Development tool promised as an eventual object-oriented, client/server replacement for CSP1 and/or VisualAge. Like CSP it allows code to be generated in one environment for execution in another. Generates COBOL, and includes a GUI interface builder.
High Speed Links: iSeries 400 interface to a server, or the loop and cables for the interface, with data transfer rates of up to 1GBps.
Hiperbatch: z/OS facility announced October 1989 to speed up common batch processing applications. Hiperbatch reduces disk and channelI/Os by placing sequential batch data into Hiperspace for the whole of a multi-job batch run. The Move Page facility is then used to transfer data between expanded and central storage. In batch processing using sequential files, data can be shared among programs. Improvements in batch performance of up to 60% are claimed by IBM.
HiPerLink: High Performance Coupling Links. One of five types of CF channels that can be used to connect a CF to an LPAR.
Hiperpool: DB2 UDB for z/OS facility (announced March 1993) which allows DB2 buffer pools to use Hiperspaces.
HiperSockets: Network in a box functionality that allows high speed any-to-any connectivity among operating system images within a zSeries 900 without requiring any physical cabling. The zSeries 900 does a direct move from one LPAR’s memory to another’s memory using QDIO.
Hipersort: See Hipersorting.
Hipersorting: DFSORT’s use of hiperspace to improve sorting performance in z/OS. Introduced in DFSORT Version 11, announced February 1989.
Hiperspace: HIgh PERformance SPACE. A range of contiguous virtual storage addresses that a z/OS program can use as a buffer, which can extend up to 2GB. Read and written exclusively in 4KB blocks. Announced February 1988. See also Hipersorting, Hiperbatch, Hiperpool.
HIPO: Hierarchy, Input, Process, Output. A development and documentation methodology commonly used by IBM for system documentation in bygone days.
HIPPI: HIgh-performance Parallel Processor Interface. An ANSI standard for attaching devices to parallel processing systems. IBM has several HIPPI implementations. September 1990 it announced a system for connecting two high-end ES/9000 processors together to create a single-system image (i.e., a single resource). HIPPI is also used in the SCSE package to support a high-speed disk array. PR/SM support for HIPPI attachment was announced September 1991. RS/6000 (pSeries) support announced July 1993. A HIPPI Protocol Support Service Program was announced for AIX October 1999. See also 9570.
HLASM: See High Level Assembler.
HLASM Toolkit: High Level ASseMbler Toolkit. See High Level Assembler.
HLL: High-Level Language. A programming language that does not reflect the structure of any particular operating system or computer machine instruction architecture.
HLLAPI: High-Level Language Application Programming Interface. An API within all of IBM’s 3270 terminal emulators that allows other programs to call the API to create 3270 format input and interpret 3270 output.
HLM: Heterogeneous LAN Management. Joint project (announced early 1993) between LAN specialist 3Com and IBM to develop a set of network management specs (based to some extent on NDIS) for mixed TRN and Ethernet systems. Uses the CMIP1 protocol.
HLMI: High-Level Machine Interface. A layer within the AS/400’s software structure. After mid 1995, the HLMI became the TIMI.
HMC: Hardware Management Console. The operator’s console on the mainframe, such as the 2074 on the eserverzSeries 900.
HMF/VM: See Host Management Facilities.
Hogan: Banking systems specialist. IBM had exclusive rights to market Hogan’s IBA products, but transferred the rights back to Hogan early 1994.
Hollywood: Presentation graphics product from Publishing Solutions Inc for the PC-DOS Windows 3.0 environment. As from July 1991 Hollywood was sold by IBM. Withdrawn January 1992.
Holographic storage: Based on the principle that certain inorganic crystals are photo-refractive, which allows optical information to be written to and read from the crystal by laser beams. Using two beams, an object beam and a reference beam, to create an interference pattern, the actual substance of a hologram gets stored as a page of defined optical characteristics. Although not commercially available, its low cost, random access and ultra-mass storage characteristics will be a prime consideration for commercial development. At one time being developed by StorageTek.
Home page: The introductory page for an InternetWeb site. This provides an introduction to the site and hypertext links to local and non-local resources or pages. For sites with their own domain names, this is what you get when you type www. followed by the domain name (e.g., www.ibm.com) into a Web browser.
Hook: A helpful way, built into software or hardware products by the original developers, to allow others to add custom features or to interface with the product.
Hop: In APPN, a portion of a route that has no intermediate nodes.
Hop count: A reference to the maximum number of nodes through which a frame may pass on the way to its destination in a Token Ring Network.
Horizontal Capacity Upgrade on Demand: An IBM Global Financing offering that sees additional processors and storage shipped in advance of actual need, and available for use as soon as the additional capacity is required. And, of course, not paid for until actually used.
Host: A computer system that is a server and/or serves attached terminals.
Host Access Client Package: The combination of Personal Communications, WebSphere Host On-Demand and Screen Customizer. Covers workstation-based viewing of 3270, 5250 and DEC VT (e.g., VT100) host terminal sessions through both Windows GUI and Web browser interfaces, as well as converting host screens into a GUI without any programming or host source code modifications.
Host integration server: Server-side middleware, with extensive connectivity options to disparate host systems, for the creation of new e-business applications that rely on the manipulation and synthesis of data from multiple, existing mission-critical applications, e.g., WebSphere Host Publisher.
Host Management Facilities: z/VM SystemView software for automated monitoring and scheduling of z/VM work. A system programmer’s and operator’s tool. Includes an OS/2 workstation GUI. aka HMF/VM. Announced September 1991. Withdrawn September 2001.
Host On-Demand: An IBM Java applet-based product that performs tn3270, tn5250 and DECVT100 emulation to enable users to access SNA and DEC applications from a Web browser. Replaced by Host Access Client Package September 2000.
HostView: Rumored name for what eventually emerged as SystemView.
Hot-plugging: IBMspeak for the ability to connect and disconnect devices in an ESCON or FICON configuration without having to close everything down. Also known as dynamic I/O reconfiguration.
HP: Hewlett-Packard Company. Founded in 1939 as an electronics company, its first product was the HP 200A, a resistance capacity audio oscillator, used to test sound equipment. In the early 1970s, developed the first hand-held calculators that engineering students were forced to buy, costing them more than a full year’s tuition. Today, a huge computer company, though they are still heavily into other electronics. See also HP-UX.
HPCS: Highly Parallel Computer Systems. IBMspeak for what emerged as the 9672R CMOS machines.
HPDT: High-Performance Data Transfer services. Functionality in VTAM that increases the efficiency of large message transfers for VTAM application programs.
HPDT interface: An API in VTAM that increases the efficiency of bulk data transfers by eliminating the data copy when data is transferred between an application program and VTAM.
HPFS: High Performance File System. An OS/2 file system that offers multiple improvements over FAT, which OS/2 also supports, at the expense of compatibility with PC-DOS or Windows. No other operating system can read an HPFS-format disk partition, so neither dual boot or partition sharing is not possible (except between two OS/2 systems). HPFS offers greater reliability, 2 to 10 times performance improvement and support for larger files. HPFS is compatible with FAT at the API level. cf. NTFS.
HPO: High Performance Option. See VM/HPO.
HPOFS: See High Performance Optical File System.
HPQS: High Performance Query System. z/OS DB2 database query system which eventually became the Parallel Query Server.
HPR: High Performance Routing. The first implementation of APPN+. Includes proactive congestion control (which minimizes re-transmissions), non-disruptive re-routing, and improved performance over standard APPN.
HPS: High Productivity System. Client/server CASE1 development environment developed by Seer Technologies and marketed by IBM to selected clients, mainly in the financial sector. HPS provides an environment for the development of cooperative applications. Includes facilities for data modeling, code generation, testing, code distribution, and software maintenance. Withdrawn July 1996.
HPSS: Highly Parallel Supercomputing Systems. See SP1, SP2.
HPT: Host Print Transform. An OS/400 function that does code translation and formatting to enable iSeries 400 print output to be spooled to PC printers.
HPTS: High Performance Transaction System. Enhancement of ImagePlus for the z/OS environment, announced November 1991. It was a joint development between IBM and a number of major banks, and was designed mainly for cheque processing. In September 1998, HPTS was sold to Check Solutions Company, a partnership between IBM and First Tennessee Bank and IBM stopped marketing it soon after.
HPTSS: High-Performance Transmission Subsystem. A high-speed line adapter that connects to the 3745 communication controller.
HSA: High-Speed Adapter. Subchannels on an eserverzSeries 900.
HSB: High-Speed Buffer.
HSC: High Speed Channel. ANSI standard for high-speed channels. IBM’s SCSE announcements in June 1989 included a 100Mbyte HSC, which can be used to link any processors (IBM or non-IBM) which implement the ANSI standard. When HSC was officially announced, it had a new name: HIPPI.
H Series: Pre-announcement code name for the 308x Series.
HSL: See High Speed Links.
HSM: Former name of DFHSM, later renamed DFSMShsm.
HSSI: ANSI standard for WANs giving up to 53Mbps over 24-pair twisted copper. Mainly used for moving large amounts of data between workstations or between processing and storage/archiving units.
HSSP: High Speed Sequential Processing. IMS1 feature which reduces contention for data by using its own buffers for database buffering.
HTF: Host Transaction Facility under DPPX on 8100.
HTML: HyperText Mark-up Language. A set of commands that are used in Web pages to format text and to establish hypertext links to other Web pages, including those on other Web sites. These commands are read and interpreted by a browser running on the client machine. An implementation of SGML, HTML is used universally across the Web, and HTML generation is widely offered as a feature of word processors, database packages, and groupware products such as LotusNotes.
HTTP: HyperText Transfer Protocol. A connectionless, layer 4 protocol used on top of IP1 for data transfer between Web servers and Web browsers. Which, of course, is why you will see http:// in front of the URL of a Web page in the address bar of a browser. Just as PC-DOS character-based terminal emulators (3270, 5250, DECVT100) were replaced with Windows GUI-based versions, applet-based versions now offer the option of using HTTP rather than tn3270, in conjunction with a Web server proxy, as a means of easily traversing firewalls using the existing firewall1 definitions for Web server access.
HTTPS: Secure HTTP. Where security in the form of SSL is superimposed on top of HTTP on a transaction-by-transaction basis. Although the little padlock icon in your browser is the only reliable indication of SSL security, seeing https:// in the address bar indicates that a secure SSL connection to the Web page was attempted.
HTTP Server: IBM Web server supported on a number of platforms, including OS/400. It is also an element of z/OS.
Hub: Generic term for a device that supports the connection of workstations and systems over various network topologies and media types. Most commonly used to refer to the central node of a star topology network which manages the network. The 8230, 8240, and 8250 are all hubs.
Hub Management Program: See IHMP.
HUON: Insurance package sold by IBM-HUON Solutions. It was one of the first to receive ClusterProven status in May 1999.
HWMCA: HardWare Management Console Application. Has several types of APIs for the Hardware Management Console (HMC), including management APIs and user interface transition APIs used by System Automation.
Hybrid EDI: Used in situations when only one trading partner is able to use EDI1, while the other continues to trade using traditional methods such as paper or fax.
Hypertext: A way of presenting information on-line with connections (called hypertext links) between one piece of information and another. Given that the HT in HTML stands for hypertext, it is no surprise that Web pages are full of hypertext links.