Glossary

AC. Alternating current. Current in which the direction is reversed, or alternated, 60 times per second (50 times per second in some countries). Contrast with direct cur- rent.

acceptance test. A formal test done by a system end- user to determine if a system works according to specifi- cations and should be accepted.

access density. A measure of I/O activity; the number of I/O operations per gigabyte of functional capacity per second.

access privileges. The extent to which a user may op- erate a system resource on a host, network, or file serv- er. In many cases, permission to access a host, network, or file server, view its contents, and modify or create files is limited by a system administrator to maintain security.

ACMI. VSM-VTSS cache memory interface card.

AC power redundancy (ACPR). An AC power system that provides dual AC power sources to prevent power interruptions and loss of access to data. If one power source fails, the other (redundant) source supplies all power to a subsystem until the failed unit is replaced.

ACS. Automated Cartridge System. Also library or tape library. A system that automatically mounts cartridges in tape drives in response to requests from host software.

ACSLS. Automated Cartridge System Library Software; Automated Cartridge System Library (Unix) Server.

actuator-level buffer (ALB). Solid-state memory asso- ciated with an actuator in a storage device. In VSM, ALBs minimize rotational latency in disk drives and allow non-synchronous data transfer between the front-end cache and back-end disk array drives.

address. (1) A hexadecimal number that represents an identifying location for a device or an area of storage; for example, a memory register, disk sector, or network node. (2) An identifier for a communication port. (3) The act of communicating with a storage device.

ADC. Analog-to-digital converter. ADT. Automatic data transfer.

AFO. Americas Field Operations. Acronym for all Sun StorageTek U.S./Canada field operations.

AIX. Advanced Interactive eXecutive. The IBM version of Unix.

ALB. See actuator-level buffer.

algorithm. A detailed, ordered set of instructions for solving a problem. When used in computer program- ming, term refers to instructions given to a computer.

allocated array cylinder. An array cylinder that contains current or non-current user data.

alphanumeric. A system of notation which utilizes al- phabetic letters, numbers, and special characters.

AME. Advanced Manufacturing Engineering. At Sun StorageTek, an engineering group that manufactures product prototype machines, typically through the EPE phase of a product development cycle.

AMT. Automatic migration threshold. User-defined per- centage values that determine when virtual tape volume migration begins and ends. VTV migration begins when the VTSS buffer reaches the high AMT and ends when the buffer reaches or falls below the low AMT. These thresholds apply to all VTSSs.

analog. A means of representing data in continuously variable physical quantities, in contrast to digital repre- sentation of data in discrete units (binary digits 1 and 0). Analog systems handle information that is represented by continuous change and flow, such as voltage or cur- rent. Contrast with digital.

ANSI. American National Standards Institute. An organi- zation that establishes procedures by which accredited organizations create and maintain voluntary industry standards in the U.S., including those for the computer industry. ANSI is the U.S. member of the International Electrotechnical Commission (IEC) and the International Organization for Standardization (ISO).

ANV. VSM-VTSS nonvolatile memory storage card. APL. Assembly parts list.

application. A software program designed to perform a specific task or group of tasks, such as word processing, communications, or database management.

array. A group of storage devices controlled in such a way as to provide higher data transfer rates, higher data availability, and data redundancy. An array is typically treated as a single volume by a host operating system.

array architecture. A class of magnetic disk architec- ture in which several physical devices emulate (typically) fewer virtual devices of (typically) higher capacity and performance.

array cylinder. A collection of all physical cylinders in a dual-redundancy array with the same physical address (CC, **). VSM allocates back-end space in units of array cylinders, which are either free or allocated.

array track. A collection of all physical tracks in a dual- redundancy array that have the same physical track ad- dress (CC, HH).

ASAL. Alternate Sector Assignment List.

ASCII. American Standard Code for Information Inter- change. A protocol for displaying characters and trans- ferring data between computers and associated equip- ment. ASCII codes are numbers from 0 to 255. Numbers 0 to 32 are non-printing control codes; 33 to 127 are for letters and punctuation; 128 to 255, called extended characters, can be used for a variety of purposes, but are most commonly used for accented letters, graphics, and other special characters.

ASIC. Application-specific integrated circuit. A custom- ized microchip designed for use on a particular circuit board, or for a specific application.

ASM. Application Storage Manager. A Sun StorageTek high-performance file system with hierarchical storage management (HSM) functionality, available for Solaris and NT platforms.

ASU. Advanced Site Unit. Hardware component of the Sun StorageTek Service Delivery Platform (SDP) remote support software.

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