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HA: See high availability. See also high-availability solution.
hacker: An unauthorized person who tries to gain access to protected resources on a system. See also cracker.
HAL: See hardware abstraction layer.
half-adjust: A method of rounding off a number by adjusting the last significant digit. When the number to the right of the last significant digit is 5 or greater, add 1 to the digit. For example, 2.475 half-adjusted to two decimal places becomes 2.48, but 2.474 becomes 2.47.
half-duplex (HD): Describing a communications connection over which only one device at a time can transmit data. See also duplex.
half-session: In SNA, one of the locations in a logical connection in a network.
halfword binary: In DB2® for IBM® i, a binary number with a precision of 15 bits.
halt indicator: In RPG, an indicator that stops the program when an unacceptable condition occurs. Valid halt indicators are H1 through H9.
handle: In application programming interfaces, a variable that represents an object, an instance of an application using some function, or a processing session.; In WebSphere® MQ, the identifier or token by which a program accesses an MQM object.
handle cursor: A pointer that keeps track of the current exception handler.
handler: A function that is registered by the application programmer to be called by the system or by the application when certain events occur in the system or application.
Hanja: Korean characters derived from Chinese.
hardcopy: A printed copy of machine output in a visually readable form, such as printed reports, documents, and summaries.
hard disk: A nonremovable storage medium used for storage of data on a personal computer.
hard link: A named connection between an object and its parent directory. An object may have multiple named connections between itself and one or more parent directories.; In a file system, an actual path to an existing object. A hard link is established by creating a directory entry. A hard link cannot cross file systems.
hardware abstraction layer (HAL): In operating systems such as Windows NT, a layer in which assembly language code is isolated. A hardware abstraction layer functions similarly to an application programming interface (API) and is used by programmers to write device-independent applications.
hardware cell: In the GDDM function, the default character box associated with a particular display.
hardware character: In the GDDM function, an alphanumeric character provided by the display station, usually from a display file.
hardware service manager: A tool for displaying and working with system hardware from both a logical and a packaging viewpoint, for debugging input/output processors (IOPs) and devices, and for fixing failing and missing hardware.
hashing: A method by which a large number of memory records are stored and can then be efficiently searched. This is accomplished through the use of a tailored index that organizes the memory records. This arrangement of records is called a hash table.
hash join: A method for joining two or more files together that uses a hash value to find the matching keys.
hash table: The arrangement of memory records.
hash value: A number that is generated from a string of text. The hash value (or simply hash), is substantially smaller than the text itself and is generated by a formula in such a way that is extremely unlikely that some other text will produce the same hash value. Hashes are used in security systems to ensure that transmitted messages have not been tampered with and also are used to access data records.
HA solution: See high-availability solution. See also high availability.
HBA: See host bus adapter.
HCF: See Host Command Facility.
HCP: See host command processor.
HCP emulation: See host command processor emulation.
HD: See half-duplex. See also duplex.
HDLC: See High-level Data Link Control.
HDR: See header label.
head: A device that reads, writes, or erases data on a storage medium.
header: Text that is formatted to be in the top margin of printed pages in a document. See also footer.; In disk management, the 8-byte portion of the 520-byte disk sector used by the operating system for control and access information.; See include statement.
header file: See include file.
header fragment: The first fragment in a series of fragments.
header label (HDR): A set of information on a or tape that describes the contents of the or tape.
header record: In RPG, output records that are printed at the top of a report and include report titles, column headings, or any other data needed to identify the information in the report.; A record that contains information, such as customer name and customer address, that is common to detail records. See also detail record.
heap: In Java™ programming, a block of memory that the Java virtual machine uses at run time to store Java objects. Java heap memory is managed by a garbage collector, which automatically de-allocates Java objects that are no longer in use.; An object that provides dynamic storage for a procedure. The object is part of the activation group and is deleted when the activation group is deleted.
heap identifier: A number that identifies a heap within its activation group.
heartbeat: A signal that one entity sends to another to convey that it is still active.
held state: The state of a connection that results in the connection being maintained after the next commit operation. This is the initial state of connections. See also released state.
help level specification: In a display file, data description specification coded between the record and field level that defines areas on the screen and associates help information with those areas.
help module: In user interface manager, the smallest part of a panel group object that can be displayed separately. A help module can be used for contextual help, extended help, or a hypertext node.
heuristic decision: A decision to force a commit or rollback of a logical unit of work in part of a transaction program network that is using the two-phase commit protocol. A heuristic decision is made when a system or communication failure prevents the logical unit of work from being completed.
hexadecimal: Pertaining to a numbering system that has a base of 16.
hexadecimal string: In REXX, any sequence of zero or more hexadecimal digits (0-9, a-f, or A-F), optionally separated by blanks, delimited by apostrophes or quotation marks, and immediately followed by the symbol x or X.
HFS: See hierarchical file system.
hidden address: An address that is mapped to another address. The method of mapping that is used does not allow external systems to initiate communications with hidden addresses unless port numbers are specified.
hidden field: A field in a display file that is passed to and from the program but is not sent to the display.
hide function: In AFP Utilities, a function on the screen view used to display elements hidden by other elements that were specified after the hidden elements and in the same or approximate position as the hidden elements.
hierarchical file system (HFS): A part of the IBM i operating system that includes the application programming interfaces and the underlying file system support. HFS enables an application written in a high-level language to create, store, retrieve, and manipulate data on a storage device. The view of the data to the user is a hierarchical directory structure similar to DOS.
hierarchical storage management (HSM): A function that automatically distributes and manages data on disk, tape, or both by regarding devices of these types and potentially others as levels in a storage hierarchy that range from fast, expensive devices to slower, cheaper, and possibly removable devices. The objectives are to minimize access time to data and maximize available media capacity. See also migrate.
hierarchy: In COBOL, a set of entries that includes all subordinate entries to the next equal- or higher-level number.
high availability (HA): The ability of IT services to withstand all outages and continue providing processing capability according to some predefined service level. Covered outages include both planned events, such as maintenance and backups, and unplanned events, such as software failures, hardware failures, power failures, and disasters. See also high-availability solution.
high-availability solution (HA solution): A combination of hardware, software, and services that fully automates the recovery process and does not disrupt user activity. HA solutions must provide an immediate recovery point with a fast recovery time. See also high availability.
High-level Data Link Control (HDLC): A form of communications line control that uses a specified series of bits rather than control characters to control data transmission over a communications line.
high-level language (HLL): A programming language that provides some level of abstraction from assembler language and independence from a particular type of machine.
high-level language pointer (HLL pointer): A source pointer that the programmer declares in the user program.
highlight: To emphasize a display element or segment by changing its visual attributes.
high-performance file system (HPFS): In PC operating systems, an installable file system that uses high-speed buffer storage, known as a cache, to provide fast access to large disk volumes. The file system also supports the coexistence of multiple, active file systems on a single personal computer, with the capability of multiple and different storage devices.
high performance optical file system (HPOFS): An IBM-developed media-format architecture that is available when initializing optical media. This media format is required for Write Once Read Many (WORM) media, and it is the default media format when initializing erasable optical media.
High-Performance Routing (HPR): An addition to APPN that enhances data-routing performance and session reliability.
high-speed line: A communications line that transmits at speeds greater than 19,200 bits per second.
high-speed link (HSL): A hardware connectivity architecture that links system processors to system I/O buses and other systems.
high-speed link loop: The system-to-tower connectivity technology that is required to implement switchable independent disk pools residing on an expansion unit (tower). The servers and towers in a cluster using resilient devices on an external tower must be on an HSL loop connecting with HSL cables.
high-speed link ring (HSL ring): A logical ring of HSL connections originating from the HSL controller of a processor unit, sequentially connecting I/O or other processor units and ending back at the HSL controller where the ring originated.
HiperSockets™: A System z® hardware feature that provides high performance internal communications between logical partitions (LPARs) within the same central processor complex (CPC) without the use of any additional or external hardware equipment such as a channel adapter.
Hiragana: One of the two common Japanese phonetic alphabets (the other is katakana). The symbols are cursive or curvilinear in style. Hiragana syllables are typically used in the representation of native Japanese words and grammatical particles. See also Katakana, Kanji.
histogram: In Performance Tools, a bar graph used in the performance advisor to display the variations over time of one type of data in a performance data collection.; In the GDDM function, a chart in which each value of the dependent variable corresponds to a range of values of the independent variable (represented by the width of the associated bar). For example, such a chart might display the number of people in various age ranges.
history log: A summary of the system activities, such as system and job information, device status, system operator messages, and a record of program temporary fix (PTF) activity on the system. The history log is identified by the name QHST, and the system-recognized identifier for the object type is *MSGQ., A summary of the system activities, such as systemand job information, device status, system operator messages, and a record of program temporary fix (PTF) activity on the system. The history log is identified by the name QHST, and the system-recognized identifier for the object type is *MSGQ.
HLL: See high-level language.
HLL pointer: See high-level language pointer.
HMC 5250 console: An emulation session to a logical partition's IBM i operating system.
hold delivery: The method of delivering messages to a message queue that holds the messages until the user requests them. The user is not notified when a message arrives.
home directory: The current directory associated with the user at the time of login.
home interface: In enterprise beans, an interface that defines zero or more create and remove methods for a session bean or zero or more create, finder, and remove methods for an entity bean.
home location: In Backup, Recovery, and Media Services, the storage location where available media is stored awaiting reuse. Typically, this is the on-site tape inventory.
home menu: The menu that is displayed if the user presses the Home key while the cursor is in the home position of a menu.
home page: The initial Web page that is returned by a Web site when a user specifies the URL for the Web site. Essentially, the home page is the entry point for accessing the contents of the Web site.
home position: The position (farthest left) to which the print head moves after the printer is turned on and the Stop or Reset button is pressed.; In System i® Access, the first position of the first input field on the display.; The first item in a list or the first line of help information.
home system: The first system in a chain of systems that are linked by any combination of TELNET and pass-through requests.
hook: A location in a compiled program where the compiler has inserted an instruction that allows programmers to interrupt the program (by setting breakpoints) for debugging purposes.
hop: One segment of a transmission path between adjacent nodes in a routed network.
horizontally displayed records: Subfile records that are grouped so that each line on the display shows more than one record of the same record format.
host: A computer that is connected to a network and provides an access point to that network. The host can be a client, a server, or both a client and server simultaneously. See also server, client.; In a cooperative processing environment, the system running the server program with which the CoOperative Development Environment/400 session communicates.; The controlling or highest-level system in a data communications configuration.; In TCP/IP, any system that has at least one Internet address associated with it.
host bus adapter (HBA): An interface card that connects a host bus, such as a peripheral component interconnect (PCI) bus, to the storage area network.
host-centric application: In VisualAge® RPG, an application in which the user's program logic is stored and run on the host.
host command: In CoOperative Development Environment/400, a command processed on a host system. It can be sent from the host emulation window or from the AD/Cycle CoOperative Development Environment session.
Host Command Facility (HCF): A feature available on a System/370, 43xx, or 30xx host system that enables a user on the host system to use applications on a System i system or other systems as if they were using remotely attached 5250-type display stations.
host command processor (HCP): The SNA logical unit of the programmable store system store controller.
host command processor emulation (HCP emulation): A function of the Point-of-Sale Utility licensed program that allows the System i system to appear to the host command processor (HCP) in a point-of-sale system as if the System i system were the System/370 host system.
hosted partition: A logical partition that is dependent on another logical partition for I/O resources. The I/O resources that a hosted partition can share include disk, CD, and tape devices.
host ID: In TCP/IP, that part of the internet address that defines the host on the network. The length of the host ID depends on the type of network class (A, B, or C).
hosting partition: Either the primary or a secondary partition that is not a guest partition. The hosting partition has the real I/O devices that the virtual I/O device drivers in a guest partition connect to. The hosting partition also supplies the guest partition's DST console session, via a TELNET connection into the hosting partition. The guest partition's console is not part of the hosting partition's console. The host partition's console, the guest partition's console session and the guest partition's operating system's console are all different console sessions.
host language: Any programming language in which SQL statements or XQuery expressions can be embedded.
host master key: In Cryptographic Support, a type of key-encrypting key used to encrypt data-encrypting keys and whose variants are used to encrypt all other key-encrypting keys stored on the system.
host master-key variant: In Cryptographic Support, a key-encrypting key derived from the host master key that is used to encrypt a certain type of cross-domain key.
host-mixed encoding scheme: An encoding scheme that contains a mixture of single-byte EBCDIC code pages and double-byte host code pages. A 5026 encoding scheme, for example, is CP290 (single byte) and CP300 (double byte).
host name: In Internet communication, the name given to a computer. Sometimes, host name is used to mean the fully qualified domain name; other times, it is used to mean the most specific subname of a fully qualified domain name. For example, if mycomputer.city.company.com is the fully qualified domain name, either of the following host names can be used: mycomputer.city.company.com or mycomputer.
host print transform (HPT): An IBM i print function that converts an SNA character string (SCS) data stream into an ASCII data stream. The conversion enables consistent ASCII printing through hardware connections.
host program: An application program that is written in a host language and that contains embedded SQL statements or XQuery expressions.
host server: Any computer on a network that is a repository for services available to other computers on the network.
host structure: In an application program, a structure that contains a list of host variables that can be referred to by embedded SQL statements.
host table: A list of host names and associated Internet Protocol (IP) addresses for an Internet Protocol (IP) network.
host variable: In an application program, a variable that is referred to by embedded SQL statements. Host variables are programming variables in the application program and are the primary mechanism for transmitting data between tables in the database and application program work areas.
hot backup: In a remote journal network, pertaining to the function of replicating an application's dependent data from one primary System i product to a backup System i product. If the primary system fails, processing can be performed on the backup system.
hot key: To jump from a host session to an application on a workstation, or from the workstation to the host session.; A key sequence used to shift operations between different applications or between different functions of an application.
hot link: In VisualAge RPG, a function used to copy information to and from Microsoft Windows programs.
hot plug: To install a hardware component without turning off the system.
hot spare: Pertaining to redundant hardware (such as an adapter, a disk, or a server) that is installed and available in the event of a hardware failure.
hot spot: An area of the display that, when clicked on, calls a macroinstruction.
HPFS: See high-performance file system.
HPOFS: See high performance optical file system.
HPR: See High-Performance Routing.
HPT: See host print transform.
HRI: See human readable interpretation.
HSL: See high-speed link.
HSL ring: See high-speed link ring.
HSM: See hierarchical storage management. See also migrate.
HTML: See Hypertext Markup Language.
HTTP: See Hypertext Transfer Protocol.
HTTP method: An action that is used by the Hypertext Transfer Protocol. HTTP methods include GET, POST, and PUT.
HTTPS: See Hypertext Transfer Protocol Secure.
HTTP Server for IBM i: A licensed program that enables a computer that uses the Hypertext Transfer Protocol (HTTP) to serve objects by responding to requests from other programs, such as browsers. The IBM HTTP Server for IBM i, which supports the Secure Sockets Layer (SSL) protocol, provides secure communications between a server and an SSL-capable browser.
hub: A half-duplex device that sums all of its input and then broadcasts that sum on all output to the connected adapters. A hub has a large collision domain and shared media.
hue: The gradual variations of colors such as blue, green, red, yellow, and so on.
human readable interpretation (HRI): In AFP Utilities, the characters printed above or below a bar code. These characters are read by people, not by scanners.
hypertext: A way of presenting information online with connections (called hypertext links) between one piece of information (called a hypertext node) and another.
hypertext link: The connection between one hypertext node and another.
Hypertext Markup Language (HTML): A markup language that conforms to the Standard Generalized Markup Language (SGML) standard and was designed primarily to support the online display of textual and graphical information, including hypertext links.
hypertext node: In a hypertext environment, a complete module of information that is linked to other relevant modules by hypertext links.
Hypertext Transfer Protocol (HTTP): An Internet protocol that is used to transfer and display hypertext and XML documents on the Web.
Hypertext Transfer Protocol Secure (HTTPS): An Internet protocol that is used by Web servers and Web browsers to transfer and display hypermedia documents securely across the Internet.
hypervisor: A program or a portion of Licensed Internal Code that allows multiple instances of operating systems to run simultaneously on the same hardware.