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access control key. Synonym for privacy key. (A)

access controller. In an information resource directory system with entity-level security, a pair of locks, one for read access, the other for write access. Locks may be used for other purposes, such as to permit execution. (A)

access control list. (1) In computer security, a collection of all access rights for one object. (2) In computer security, a list associated with an object that identifies all the subjects that can access the object and their access rights; for example, a list associated with a file that identifies users who can access the file and identifies their access rights to that file. See capability list. (3) In the AIX operating system, a file attribute that contains the basic and extended permissions that control access to the file. (4) In the AIX operating system, a list of hosts, maintained by Enhanced X-Windows, that have access to client programs. By default, only programs on the local host and those in this list can use the display. The list can be changed by clients on the local host; some server implementations can also modify the list. The authorization protocol name and data received by the server at connection setup may also affect this list. Synonymous with access list.

access control lock. Synonym for privacy lock. (A)

Access Control -- Logging and Reporting. In VSE, an IBM licensed program used to log access to protected data and to print selected formatted reports on such access.

access environment. A description of the current user, including user ID, current connect group, user attributes, and group authorities. An access environment is constructed during user identification and verification.

access key. In an information resource directory system with entity-level security, an authorization to perform a set of operations on an entity secured by a lock. (A)

access level. (1) In computer security, the level of authority a subject has when using a protected resource; for example, authority to access a particular security level of information. (2) In computer security, the hierarchical portion of the security level used to identify the sensitivity of data and the clearance or authorization of users. (3) In the IBM LinkWay product, the characteristic of a folder that determines how much a user can modify the folder. The access level is determined by the person who creates the folder.

access line. A telecommunication line that continuously connects a remote station to a data switching exchange (DSE). A telephone number is associated with the access line.

access list. Synonym for access control list. See also standard access list.

access lock. Synonym for privacy lock. (A)

access macro. A macroinstruction that establishes the linkage between a program requesting execution of a system routine and the system routine requested.

access matrix. In computer security, a two-dimensional array, one dimension of which represents objects and the other dimension subjects, where the intersections represent permitted access types.

access mechanism. (1) A mechanism responsible for moving an access arm or a comb. Synonymous with actuator. (T) (2) A group of access arms that move together as a unit.

Figure 2. Access Mechanism

access method. (1) A technique to obtain the use of data, storage, or the use of an input/output channel to transfer data; for example, random access method, sequential access method. (T) (2) The technique that is used to locate data stored on a physical medium. (A) (3) A technique for moving data between main storage and input/output devices. (4) The way that a system refers to records in files; the reference can be consecutive (records are referred to one after another in the order in which they appear in the file) or it can be random (the individual records are referred to in any order).

access method control block (ACB). A control block that links an application program to VSAM or VTAM programs.

access method interface (AMI). The TCAM function for managing communication on the access method control block (ACB) interface between TCAM and VTAM programs.

access method routines. Routines that move data between main storage and input/output devices.

access method services (AMS). The facility used to define and reproduce VSAM key-sequenced data sets (KSDS).

access mode. (1) A technique that is used to obtain a particular logical record from, or to place a particular logical record into, a file assigned to a mass storage device. (A) (2) The manner in which files are referred to by a computer. Access can be sequential (records are referred to one after another in the order in which they appear on the file), access can be random (the individual records can be referred to in a nonsequential manner), or access can be dynamic (records can be accessed sequentially or randomly, depending on the form of the input/output request). (3) In COBOL, the manner in which records are to be operated upon within a file. (4) See file access mode. See also random access, sequential access.

access name. (1) In a database, a name that identifies an entity. (2) In an information resource dictionary, the name by which an entity is known to the user interfaces. It is the combination of an assigned access name and version identifier that together serve as the primary identifier of each entity. (A)

accessor. (1) In computer security, any user of a protected resource. (2) In MSS, the component of the IBM 3851 Mass Storage Facility that transports data cartridges between the cartridge cells, data recording devices, and the cartridge access station.

accessor control. In MSS, the component of the IBM 3851 Mass Storage Facility that decodes and sequences messages from the mass storage control and directs the motion of the accessor.

accessor environment element (ACEE). In RACF, a description of the current user including userid, current connect group, user attributes, and group authorities. An ACEE is constructed during user identification and verification.

accessory. (1) A basic part, subassembly, or assembly used with another assembly, unit, or set. (2) A separately orderable part that has no type number, is for purchase only, and does not receive normal IBM maintenance.

access path. (1) A sequence of data items used by a database management system to access records or other data items stored in a database. There may simultaneously exist more than one access path for one data item. (T) (2) A chain of addresses that leads to the desired data. (A) (3) The procedure used by a database management system to access data stored in a database. (A) (4) The order in which records in a database file are organized for processing by a program. See arrival sequence access path, keyed sequence access path. (5) In SQL, the path used to locate data specified in SQL statements. An access path can be indexed, sequential, or a combination of both.

access path independence. The independence of logical data descriptions on access paths. Programs using access path independent logical data descriptions need not be changed when access paths are changed. (T)

access path journaling. A method of recording changes to an access path as changes are made to the data in the database file so that the access path can be recovered automatically by the system.

access period. In computer security, a period of time during which specified access rights prevail.

access permission. (1) All of a user's access rights. (A) (2) All access rights a user has regarding an object. (I) (3) In the AIX operating system, a group of designations that determine who can access a particular file and how the user can access the file. See base permission, extended permission. See also permission code.

access plan. In SQL, the control structure produced during compile time that is used to process SQL statements encountered when the program is run.

access priority. In the IBM Token-Ring Network, the maximum priority that a token can have for transmission via the token-ring adapter.

access procedure. The procedure or protocol used to gain access to a shared resource; for example, in a local area network the shared resource is the transmission medium. The medium access procedures specified by the IEEE 802 standard are CSMA/CD token, bus, and ring.

access right. (1) In computer security, permission for a subject to use an access type for a particular object; for example, permission for a process to read a file. (2) The right to use a defined computer resource such as a library or file. (3) Synonymous with permission.

access time. (1) The time interval between the instant at which a call for data is initiated and the instant at which the delivery of data is completed. Access time equals latency plus transfer time. (T) (2) Deprecated term for cycle time. (3) See seek time. See also latency. Contrast with response time.

Figure 3. Time Intervals for Accessing Data

access type. In computer security, a kind of access to an object; for example, access to read a file, access to write in a file, access to delete a file.

access unit. In an IBM Token-Ring Network, a wiring concentrator. See multistation access unit.

account. In the AIX operating system, the login directory and other information that gives a user access to the system.

accountability. In computer security, the property that enables activities on a system to be traced to individuals who may then be held responsible for their actions.

accountability information. An audit trail for security purposes.

account file. A direct access file maintained by VSE/POWER to hold the accounting information it generates and the programs that it controls.

accounting check digit. See self-check digit.

accounting code. In the AS/400 system and System/38, a 15-character field, assigned to a job by the system when it is processed by the system, that is used to collect statistics for the system resources used for that job when job accounting is active.

accounting entry. In the AS/400 system and System/38, a journal entry that contains statistics of system resources used for job accounting.

accounting level. In the AS/400 system and System/38, a system value identifying the type of data to be recorded when job accounting is active.

accounting machine. (1) A keyboard-actuated mach- ine that prepares accounting records. (A) (2) A machine that reads data from external storage media, such as cards or tapes, and automatically produces accounting records or tabulations, usually on continuous forms. (A)

accounting segment. In the AS/400 system and System/38, the period of time during which statistics are gathered, beginning when the job starts or when the job's accounting code is changed, and ending when the job ends or when the job's accounting code is next changed.

accounting system. A part of the AIX operating system for RISC System/6000 that monitors various aspects of system operations; it collects detailed data on each transaction and provides tools for processing the data in order to produce different kinds of reports.

account number. (1) In the IBM 3600 Finance Communication System, a number assigned by a financial institution to a particular customer account. See customer identification number. See also personal code, primary account. number. (A)

accreditation. In computer security, the authorization that is granted to an information system to process sensitive information in its operational environment.

Note: Accreditation is based on a comprehensive security evaluation of system hardware, firmware, and software security design, its configuration and implementation, and administrative, communications, personnel, physical, and procedural security controls.

accumulate (ACC). (1) To collect, for example, the values in a field. (2) To enter the result of an operation in an accumulator.

accumulating. The process of totaling values in a particular field as records are being processed.

accumulator. (1) A register in which one operand of an operation can be stored and subsequently replaced by the result of that operation. (T) (2) In the IBM 3800 Printing Subsystem Models 3 and 8, a feature that supplies a separate storage that can hold data in raster form. It can be used either for composing a sheet of data that combines a large amount of variable and constant data, or for storing an electronic overlay in raster form that will be merged with variable data as the sheet is printed.

accuracy. (1) A quality of that which is free of error. (A) (2) A qualitative assessment of freedom from error, with a high assessment corresponding to a small error. (I) (A) (3) Contrast with precision.

accuracy control character. A control character used to indicate whether the data with which it is associated are in error, or are to be disregarded, or cannot be represented on a particular device. (A) Synonymous with error control character.

ACD. Automatic call distribution.

AC/DC ringing. A method of telephone ringing that uses alternating current to operate a ringer and direct current to actuate a relay that stops the ringing when the called party answers.

ACD group. In telephony, the set of multiple agents assigned to process incoming telephone calls that are directed to the same dialed number. The routing of incoming calls to one of the agents in the ACD group is based on such properties as availability of the agent and the length of time since the agent completed the last incoming call.

ACDI. Asynchronous Communications Device Interface.

ACD pilot number. In telephony, the common telephone number that calling parties can dial to route calls to one of multiple agents.

ACEE. Accessor environment element.

ACF. Advanced Communications Function.

ACF/NCP. Advanced Communications Function for the Network Control Program. See Network Control Program (NCP).

ACF/SSP. Advanced Communications Function for the System Support Programs. See System Support Program Product.

ACF/TAP. Advanced Communications Function for the Trace Analysis Program. See Trace Analysis Program (TAP).

ACF/TCAM. Advanced Communications Function for the Telecommunications Access Method. See Telecommunications Access Method (TCAM).

ACF/VTAM product. Advanced Communications Function for the Virtual Telecommunications Access Method product. See Virtual Telecommunications Access Method (VTAM) product.

ACF/VTAME. Advanced Communications Function for the Virtual Telecommunications Access Method Entry. See Virtual Telecommunications Access Method Entry (VTAME).

"A" Change. The correction of an error in transcribing information from approved EC documents to formal documents; the issuing agency releases a new notice page and correcting documents under the same EC number with an alphabetic suffix; for example, 750123A.

ACK. The acknowledge character. (A)

acknowledge. (1) To answer. To respond to a poll, address, or message. (2) In the X.25 API, to confirm that a data packet with the D-bit set has arrived.

acknowledge character (ACK). A transmission control character transmitted by a station as an affirmative response to the station with which the connection has been set up. (I) (A) See negative-acknowledge character.

acknowledged mail. A function that allows a user to request and receive an acknowledgment that the mail item he sent was received.

acknowledged service. In communications, the service that provides for the establishment of a data link level connection. Acknowledged service provides for functions such as sequencing, flow control, and error recovery. SNA requires the use of acknowledged services.

acknowledge timeout. The number of seconds that a station should wait for an acknowledgment from a remote station after sending data.

acknowledgment. (1) The transmission, by a receiver, of acknowledge characters as an affirmative response to a sender. (T) (2) An indication that an item sent was received.

acknowledgment character. Deprecated term for acknowledge character.

ACK0. (1) A transmission control character for even positive acknowledgment. (2) In BSC, the even-numbered positive acknowledge character.

Note: The ACK0 character indicates that text was received without transmission errors. In BSC text transmission, ACK0 is used alternately with ACK1 to perform sequence validation.

ACK1. (1) A transmission control character for odd positive acknowledgment. (2) In BSC, the odd-numbered positive acknowledge character.

Note: The ACK1 character indicates that text was received without transmission errors. In BSC text transmission, ACK1 is used alternately with ACK0 to perform sequence validation.

ACM. Association for Computing Machinery.

ACO. Automated console operations.

************** AL ***************** Next

acoustic coupler. A device that interconnects a communicating unit with a telephone handset by converting sound signals to or from electrical signals. (A)

acoustic delay line. A delay line whose operation is based on the time of propagation of sound waves in a given medium. (A) Synonymous with sonic delay line.

acoustic emanations. In computer security, sound inadvertently transmitted from information processing equipment that might permit unauthorized access to information. See compromising emanations.

acoustic impulse. A brief excursion of the sound pressure level. See also impulsive noise.

acoustic memory. Synonym for acoustic storage.

acoustic panel. A panel bonded with a material to reduce operating noise from the devices in a rack.

acoustic storage. A storage device consisting of acoustic delay lines. (A) Synonymous with acoustic memory.

acquire. (1) In MSS, to allocate space on a staging drive and to stage the volume table of contents from a cartridge to the staging drive. (2) In System/36, to assign a display station or session to a program. (3) In VTAM programs , to take over resources that were formerly controlled by an access method in another domain, or to resume control of resources that were controlled by that domain but released. Contrast with release. See also resource takeover. (4) In a VTAM application program, to initiate and establish a session with another logical unit (LU). The acquire process begins when the application program issues a macroinstruction. See also accept.