IBM Books

Managing Shared Disks

Glossary of Terms and Abbreviations


Access Control List. A list that defines who has permission to access certain services; that is, for whom a server may perform certain tasks. This is usually a list of principals with the type of access assigned to each.

An adapter is a mechanism for attaching parts. For example, an adapter could be a part that electrically or physically connects a device to a computer or to another device. In the SP system, network connectivity is supplied by various adapters, some optional, that can provide connection to I/O devices, networks of workstations, and mainframe networks. Ethernet, FDDI, token-ring, HiPPI, SCSI, FCS, and ATM are examples of adapters that can be used as part of an SP system.

A character or group of characters that identifies a register, a device, a particular part of storage, or some other data source or destination.

A distributed file system that provides authentication services as part of its file system creation.

Abbreviation for Advanced Interactive Executive, IBM's licensed version of the UNIX operating system. AIX is particularly suited to support technical computing applications, including high function graphics and floating point computations.

Application Programming Interface. A set of programming functions and routines that provide access between the Application layer of the OSI seven-layer model and applications that want to use the network. It is a software interface.

The use to which a data processing system is put; for example, a payroll application, an airline reservation application.

application data
The data that is produced using an application program.

Address Resolution Protocol.

Asynchronous Transfer Mode. (See TURBOWAYS 100 ATM Adapter.)

The process of validating the identity of either a user of a service or the service itself. The process of a principal proving the authenticity of its identity.

The process of obtaining permission to access resources or perform tasks. In SP security services, authorization is based on the principal identifier. The granting of access rights to a principal.

authorization file
A type of ACL (access control list) used by the IBM AIX remote commands and the IBM PSSP Sysctl and Hardmon components.


batch processing
(1) The processing of data or the accomplishment of jobs accumulated in advance in such a manner that each accumulation thus formed is processed or accomplished in the same run. (2) The processing of data accumulating over a period of time. (3) Loosely, the execution of computer programs serially. (4) Computer programs executed in the background.

The AIX Base Operating System.


call home function
The ability of a system to call the IBM support center and open a PMR to have a repair scheduled.

Common Desktop Environment. A graphical user interface for UNIX.

charge feature
An optional feature for either software or hardware for which there is a charge.

Command Line Interface.

(1) A function that requests services from a server and makes them available to the user. (2) A term used in an environment to identify a machine that uses the resources of the network.

Centralized Management Interface provides a series of SMIT menus and dialogues used for defining and querying the SP system configuration.

Concurrent Virtual Shared Disk
A virtual shared disk that can be concurrently accessed by more than one server.

A communication process that takes place without first establishing a connection.

connectionless network
A network in which the sending logical node must have the address of the receiving logical node before information interchange can begin. The packet is routed through nodes in the network based on the destination address in the packet. The originating source does not receive an acknowledgment that the packet was received at the destination.

control workstation
A single point of control allowing the administrator or operator to monitor and manage the SP system using the IBM AIX Parallel System Support Programs.

A protocol message, or part thereof, containing a ticket and an authenticator supplied by a client and used by a server to verify the client's identity.

Communication subsystem.


A process, not associated with a particular user, that performs system-wide functions such as administration and control of networks, execution of time-dependent activities, line printer spooling and so forth.

Direct Access Storage Device. Storage for input/output data.

Distributed Computing Environment.

distributed file system. A subset of the IBM Distributed Computing Environment.

Domain Name Service. A hierarchical name service which maps high level machine names to IP addresses.


Error Notification Object
An object in the SDR that is matched with an error log entry. When an error log entry occurs that matches the Notification Object, a user-specified action is taken.

Enterprise Systems Connection. The ESCON channel connection allows the RS/6000 to communicate directly with a host System/390; the host operating system views the system unit as a control unit.

(1) Ethernet is the standard hardware for TCP/IP local area networks in the UNIX marketplace. It is a 10-megabit per second baseband type LAN that allows multiple stations to access the transmission medium at will without prior coordination, avoids contention by using carrier sense and deference, and resolves contention by collision detection (CSMA/CD). (2) A passive coaxial cable whose interconnections contain devices or components, or both, that are all active. It uses CSMA/CD technology to provide a best-effort delivery system.

Ethernet network
A baseband LAN with a bus topology in which messages are broadcast on a coaxial cabling using the carrier sense multiple access/collision detection (CSMA/CD) transmission method.

In Event Management, the notification that an expression evaluated to true. This evaluation occurs each time an instance of a resource variable is observed.

Programmed dialogue with interactive programs.

In Event Management, the relational expression between a resource variable and other elements (such as constants or the previous value of an instance of the variable) that, when true, generates an event. An example of an expression is X < 10 where X represents the resource variable IBM.PSSP.aixos.PagSp.%totalfree (the percentage of total free paging space). When the expression is true, that is, when the total free paging space is observed to be less than 10%, the Event Management subsystem generates an event to notify the appropriate application.


Also called fallover, the sequence of events when a primary or server machine fails and a secondary or backup machine assumes the primary workload. This is a disruptive failure with a short recovery time.

fall back
Also called fallback, the sequence of events when a primary or server machine takes back control of its workload from a secondary or backup machine.

Fiber Distributed Data Interface.

First Failure Data Capture.

Fiber Distributed Data Interface (FDDI)
An American National Standards Institute (ANSI) standard for 100-megabit-per-second LAN using optical fiber cables. An FDDI local area network (LAN) can be up to 100 km (62 miles) and can include up to 500 system units. There can be up to 2 km (1.24 miles) between system units and concentrators.

A set of related records treated as a unit, for example, in stock control, a file could consist of a set of invoices.

file name
A CMS file identifier in the form of 'filename filetype filemode' (like: TEXT DATA A).

file server
A centrally located computer that acts as a storehouse of data and applications for numerous users of a local area network.

File Transfer Protocol (FTP)
The Internet protocol (and program) used to transfer files between hosts. It is an application layer protocol in TCP/IP that uses TELNET and TCP protocols to transfer bulk-data files between machines or hosts.

First Failure Data Capture (FFDC)
A set of utilities used for recording persistent records of failures and significant software incidents. It provides a means of associating failures to one another, thus allowing software to link effects of a failure to their causes and thereby facilitating discovery of the root cause of a failure.

foreign host
Any host on the network other than the local host.

File transfer protocol.


An intelligent electronic device interconnecting dissimilar networks and providing protocol conversion for network compatibility. A gateway provides transparent access to dissimilar networks for nodes on either network. It operates at the session presentation and application layers.


High Availability Cluster Multi-Processing for AIX.

High Availability Control Workstation function, based on HACMP, provides for a backup control workstation for the SP system.

Hardware Management Console (HMC)
The IBM Hardware Management Console for pSeries is an installation and service support processor that runs only the HMC software. For an IBM e(logo)server pSeries 690 server to run the PSSP software, an HMC is required with a network connection to the PSSP control workstation . The HMC provides the following functions for the p690 server:

Hashed Shared Disk (HSD)
The data striping device for the IBM Virtual Shared Disk. The device driver lets application programs stripe data across physical disks in multiple IBM Virtual Shared Disks, thus reducing I/O bottlenecks.

help key
In the SP graphical interface, the key that gives you access to the SP graphical interface help facility.

High Availability Cluster Multi-Processing
An IBM facility to cluster nodes or components to provide high availability by eliminating single points of failure.

High Performance Parallel Interface. RS/6000 units can attach to a HiPPI network as defined by the ANSI specifications. The HiPPI channel supports burst rates of 100 Mbps over dual simplex cables; connections can be up to 25 km in length as defined by the standard and can be extended using third-party HiPPI switches and fiber optic extenders.

home directory
The directory associated with an individual user.

A computer connected to a network, and providing an access method to that network. A host provides end-user services.

Hardware Management Console.


instance vector
Obsolete term for resource identifier.

Intermediate Switch Board
Switches mounted in the switch expansion frame.

A specific inter-network consisting of large national backbone networks such as APARANET, MILNET, and NSFnet, and a myriad of regional and campus networks all over the world. The network uses the TCP/IP protocol suite.

Internet Protocol (IP)
(1) A protocol that routes data through a network or interconnected networks. IP acts as an interface between the higher logical layers and the physical network. This protocol, however, does not provide error recovery, flow control, or guarantee the reliability of the physical network. IP is a connectionless protocol. (2) A protocol used to route data from its source to it destination in an Internet environment.

IP address
A 32-bit address assigned to devices or hosts in an IP internet that maps to a physical address. The IP address is composed of a network and host portion.

Intermediate Switch Board.


A service for authenticating users in a network environment.

The core portion of the UNIX operating system which controls the resources of the CPU and allocates them to the users. The kernel is memory-resident, is said to run in "kernel mode" and is protected from user tampering by the hardware.

Kernel Low-Level Application Programming Interface (KLAPI)
KLAPI provides transport service for communication using the SP Switch.


(1) Acronym for Local Area Network, a data network located on the user's premises in which serial transmission is used for direct data communication among data stations. (2) Physical network technology that transfers data a high speed over short distances. (3) A network in which a set of devices is connected to another for communication and that can be connected to a larger network.

Low-level Communication API.

local host
The computer to which a user's terminal is directly connected.

log database
A persistent storage location for the logged information.

log event
The recording of an event.

log event type
A particular kind of log event that has a hierarchy associated with it.

The writing of information to persistent storage for subsequent analysis by humans or programs.

Low-level Communication API (LAPI)
A low-level (low overhead) message passing protocol that uses a one-sided active message style interface to transfer messages between processes. LAPI is an IBM proprietary interface designed to exploit the SP switch adapters.


To use a pattern of characters to control retention or elimination of portions of another pattern of characters.

A display of a list of available functions for selection by the user.

Message Passing Interface (MPI)
An industry standard message passing protocol that typically uses a two-sided send-receive model to transfer messages between processes.

The graphical user interface for OSF, incorporating the X Window System. Also called OSF/Motif.

Message Passing Interface.

Mean time between failure. This is a measure of reliability.

Mean time to repair. This is a measure of serviceability.


naive application
An application with no knowledge of a server that fails over to another server. Client to server retry methods are used to reconnect.

An interconnected group of nodes, lines, and terminals. A network provides the ability to transmit data to and receive data from other systems and users.

Network Interface Module (NIM)
A process used by the Topology Services daemon to monitor each network interface.

Network File System. NFS allows different systems (UNIX or non-UNIX), different architectures, or vendors connected to the same network, to access remote files in a LAN environment as though they were local files.

(1) Network Installation Management is provided with AIX to install AIX on the nodes. (2) Network Interface Module is a process used by the Topology Services daemon to monitor each network interface.

NIM client
An AIX system installed and managed by a NIM master. NIM supports three types of clients:

NIM master
An AIX system that can install one or more NIM clients. An AIX system must be defined as a NIM master before defining any NIM clients on that system. A NIM master managers the configuration database containing the information for the NIM clients.

NIM object
A representation of information about the NIM environment. NIM stores this information as objects in the NIM database. The types of objects are:

Network Information System.

In a network, the point where one or more functional units interconnect transmission lines. A computer location defined in a network. The SP system can house several different types of nodes for both serial and parallel processing. These node types can include thin nodes, wide nodes, 604 high nodes, as well as other types of nodes both internal and external to the SP frame.

Node Switch Board
Switches mounted on frames that contain nodes.

Node Switch Board.

Network Time Protocol.


Object Data Manager. In AIX, a hierarchical object-oriented database for configuration data.


parallel environment
A system environment where message passing or SP resource manager services are used by the application.

Parallel Environment
A licensed IBM program used for message passing applications on the SP or RS/6000 platforms.

parallel processing
A multiprocessor architecture which allows processes to be allocated to tightly coupled multiple processors in a cooperative processing environment, allowing concurrent execution of tasks.

(1) A variable that is given a constant value for a specified application and that may denote the application. (2) An item in a menu for which the operator specifies a value or for which the system provides a value when the menu is interpreted. (3) A name in a procedure that is used to refer to an argument that is passed to the procedure. (4) A particular piece of information that a system or application program needs to process a request.

See system partition.

Practical Extraction and Report Language.

The primary window for each SP Perspectives application, so called because it provides a unique view of an SP system.

A UNIX utility allowing the output of one command to be the input of another. Represented by the | symbol. It is also referred to as filtering output.

Problem Management Report.

Formerly Parallel Operating Environment, now Parallel Environment for AIX.

(1) An end point for communication between devices, generally referring to physical connection. (2) A 16-bit number identifying a particular TCP or UDP resource within a given TCP/IP node.

Obsolete term for expression.

Primary node or machine
(1) A device that runs a workload and has a standby device ready to assume the primary workload if that primary node fails or is taken out of service. (2) A node on the switch that initializes, provides diagnosis and recovery services, and performs other operations to the switch network. (3) In IBM Virtual Shared Disk function, when physical disks are connected to two nodes (twin-tailed), one node is designated as the primary node for each disk and the other is designated the secondary, or backup, node. The primary node is the server node for IBM Virtual Shared Disks defined on the physical disks under normal conditions. The secondary node can become the server node for the disks if the primary node is unavailable (off-line or down).

Problem Management Report
The number in the IBM support mechanism that represents a service incident with a customer.

(1) A unique, finite course of events defined by its purpose or by its effect, achieved under defined conditions. (2) Any operation or combination of operations on data. (3) A function being performed or waiting to be performed. (4) A program in operation. For example, a daemon is a system process that is always running on the system.

A set of semantic and syntactic rules that defines the behavior of functional units in achieving communication.


Redundant array of independent disks.

rearm expression
In Event Management, an expression used to generate an event that alternates with an original event expression in the following way: the event expression is used until it is true, then the rearm expression is used until it is true, then the event expression is used, and so on. The rearm expression is commonly the inverse of the event expression (for example, a resource variable is on or off). It can also be used with the event expression to define an upper and lower boundary for a condition of interest.

rearm predicate
Obsolete term for rearm expression.

remote host
See foreign host.

In Event Management, an entity in the system that provides a set of services. Examples of resources include hardware entities such as processors, disk drives, memory, and adapters, and software entities such as database applications, processes, and file systems. Each resource in the system has one or more attributes that define the state of the resource.

resource identifier
In Event Management, a set of elements, where each element is a name/value pair of the form name=value, whose values uniquely identify the copy of the resource (and by extension, the copy of the resource variable) in the system.

resource monitor
A program that supplies information about resources in the system. It can be a command, a daemon, or part of an application or subsystem that manages any type of system resource.

resource variable
In Event Management, the representation of an attribute of a resource. An example of a resource variable is IBM.AIX.PagSp.%totalfree, which represents the percentage of total free paging space. IBM.AIX.PagSp specifies the resource name and %totalfree specifies the resource attribute.

Restricted Root Access (RRA)
Restricted root access (RRA) limits the uses of the rsh and rcp commands within PSSP software. When RRA is enabled, it restricts root rsh and rcp authorizations from the nodes to the control workstation, and from one node to another. However, control workstation to node rsh and rcp access is still permitted.

Reduced Instruction Set Computing (RISC), the technology for today's high performance personal computers and workstations, was invented in 1975. Uses a small simplified set of frequently used instructions for rapid execution.

rlogin (remote LOGIN)
A service offered by Berkeley UNIX systems that allows authorized users of one machine to connect to other UNIX systems across a network and interact as if their terminals were connected directly. The rlogin software passes information about the user's environment (for example, terminal type) to the remote machine.

Acronym for Remote Procedure Call, a facility that a client uses to have a server execute a procedure call. This facility is composed of a library of procedures plus an XDR.

Restricted Root Access.

A variant of RLOGIN command that invokes a command interpreter on a remote UNIX machine and passes the command line arguments to the command interpreter, skipping the LOGIN step completely. See also rlogin.


Small Computer System Interface.

Secondary node
In IBM Virtual Shared Disk function, when physical disks are connected to two nodes (twin-tailed), one node is designated as the primary node for each disk and the other is designated as the secondary, or backup, node. The secondary node acts as the server node for the IBM Virtual Shared disks defined on the physical disks if the primary node is unavailable (off-line or down).

(1) A function that provides services for users. A machine may run client and server processes at the same time. (2) A machine that provides resources to the network. It provides a network service, such as disk storage and file transfer, or a program that uses such a service. (3) A device, program, or code module on a network dedicated to providing a specific service to a network. (4) On a LAN, a data station that provides facilities to other data stations. Examples are file server, print server, and mail server.

The shell is the primary user interface for the UNIX operating system. It serves as command language interpreter, programming language, and allows foreground and background processing. There are three different implementations of the shell concept: Bourne, C and Korn.

Small Computer System Interface (SCSI)
An input and output bus that provides a standard interface for the attachment of various direct access storage devices (DASD) and tape drives to the RS/6000.

Small Computer Systems Interface Adapter (SCSI Adapter)
An adapter that supports the attachment of various direct-access storage devices (DASD) and tape drives to the RS/6000.

The System Management Interface Toolkit is a set of menu driven utilities for AIX that provides functions such as transaction login, shell script creation, automatic updates of object database, and so forth.

Simple Network Management Protocol. (1) An IP network management protocol that is used to monitor attached networks and routers. (2) A TCP/IP-based protocol for exchanging network management information and outlining the structure for communications among network devices.

(1) An abstraction used by Berkeley UNIX that allows an application to access TCP/IP protocol functions. (2) An IP address and port number pairing. (3) In TCP/IP, the Internet address of the host computer on which the application runs, and the port number it uses. A TCP/IP application is identified by its socket.

standby node or machine
A device that waits for a failure of a primary node in order to assume the identity of the primary node. The standby machine then runs the primary's workload until the primary is back in service.

Shortened form of subnetwork.

subnet mask
A bit template that identifies to the TCP/IP protocol code the bits of the host address that are to be used for routing for specific subnetworks.

Any group of nodes that have a set of common characteristics, such as the same network ID.

A software component that is not usually associated with a user command. It is usually a daemon process. A subsystem will perform work or provide services on behalf of a user request or operating system request.

Software Update Protocol.

switch capsule
A group of SP frames consisting of a switched frame and its companion non-switched frames.

Secure System Command Execution Tool. An authenticated client/server system for running commands remotely and in parallel.

A BSD logging system used to collect and manage other subsystem's logging data.

System Administrator
The user who is responsible for setting up, modifying, and maintaining the SP system.

system partition
A group of nonoverlapping nodes on a switch chip boundary that act as a logical SP system.


Tape ARchive, is a standard UNIX data archive utility for storing data on tape media.

Tool Command Language.

Tool Command Language Extended.

Acronym for Transmission Control Protocol, a stream communication protocol that includes error recovery and flow control.

Acronym for Transmission Control Protocol/Internet Protocol, a suite of protocols designed to allow communication between networks regardless of the technologies implemented in each network. TCP provides a reliable host-to-host protocol between hosts in packet-switched communications networks and in interconnected systems of such networks. It assumes that the underlying protocol is the Internet Protocol.

Terminal Emulation Protocol, a TCP/IP application protocol that allows interactive access to foreign hosts.

An encrypted protocol message used to securely pass the identity of a user from a client to a server.

Tcl-based Tool Kit for X Windows.

Tape Management Program Control Point.

(1) Network technology that controls media access by passing a token (special packet or frame) between media-attached machines. (2) A network with a ring topology that passes tokens from one attaching device (node) to another. (3) The IBM Token-Ring LAN connection allows the RS/6000 system unit to participate in a LAN adhering to the IEEE 802.5 Token-Passing Ring standard or the ECMA standard 89 for Token-Ring, baseband LANs.

An exchange between the user and the system. Each activity the system performs for the user is considered a transaction.

transceiver (transmitter-receiver)
A physical device that connects a host interface to a local area network, such as Ethernet. Ethernet transceivers contain electronics that apply signals to the cable and sense collisions.

To send data from one place and to receive the data at another place. Synonymous with move.

The sending of data from one place for reception elsewhere.

An IBM high-performance, high-function intelligent adapter that provides dedicated 100 Mbps ATM (asynchronous transfer mode) connection for high-performance servers and workstations.


User Datagram Protocol.

UNIX operating system
An operating system developed by Bell Laboratories that features multiprogramming in a multiuser environment. The UNIX operating system was originally developed for use on minicomputers, but has been adapted for mainframes and microcomputers. Note: The AIX operating system is IBM's implementation of the UNIX operating system.

Anyone who requires the services of a computing system.

User Datagram Protocol (UDP)
(1) In TCP/IP, a packet-level protocol built directly on the Internet Protocol layer. UDP is used for application-to-application programs between TCP/IP host systems. (2) A transport protocol in the Internet suite of protocols that provides unreliable, connectionless datagram service. (3) The Internet Protocol that enables an application programmer on one machine or process to send a datagram to an application program on another machine or process.

user ID
A nonnegative integer, contained in an object of type uid_t, that is used to uniquely identify a system user.


Virtual Shared Disk, IBM
The function that allows application programs executing at different nodes of a system partition to access a raw logical volume as if it were local at each of the nodes. In actuality, the logical volume is local at only one of the nodes (the server node).


(1) A configuration of input/output equipment at which an operator works. (2) A terminal or microcomputer, usually one that is connected to a mainframe or to a network, at which a user can perform applications.


X Window System
A graphical user interface product.

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