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Active Control Data Set (ACDS) is a VSAM linear data set containing the SMS active source control data set (SCDS). See SCDS.

Autoloader is a device with (usually only) a single transport that can automatically load and unload the transport with one of the cartridges in its library. It can operate either in sequential mode, or in random mode under the control of library software.

ADSTAR Distributed Storage Manager (ADSM), now called Tivoli Storage Manager, is an IBM software product that enables users to manage storage, data access and backup across multivendor enterprisewide networks.

Advanced Lossless Data Compression (ALDC) is a data compression algorithm that provides substantially greater compression efficiency than IDRC or DLZ. See IDRC.

Aggregate group Backup And Recovery Support (ABARS) is an SMS tool that backs up related data sets with identical backup attributes (such as type of storage medium, retention period, or destination) that have been pooled to meet a defined backup or recovery strategy.

Automatic Cartridge Facility (ACF) contains 10-cartridges and functions as a low-cost tape library.

Automated Cartridge Systems (ACS) comprise cartridge storage cells, transports, and some kind of robotic mechanism(s) to move the cartridges between the cells and either a transport or a pass-through port to another ACS. Most automated libraries use a bar-code reader to read the external label on the cartridge. See ATL.

Automatic Class Selection (ACS) routines automatically assign an SMS-managed data set to a storage class based upon the data set's characteristics. See SMS.

Automated Tape Library (ATL) is an alternative term for Automated Cartridge System. See ACS.

Bits Per Inch (BPI) is the number of bits that can be written onto one inch of a track on a disk surface. Usually specified for worst case, which is the inner track.

Cartridge Access Port (CAP) is a 20 to 30 cartridge enter/eject facility for a StorageTek robotic tape library. See ECAP.

Cartridge System Tape (CST) is a standard length tape cartridge with a nominal uncompressed capacity of approximately 400 Mbytes.

Cartridge Tape Subsystem (CTS) forms the data path between the cartridge library and the host system. It includes tape control units and tape cartridge transports.

Computer Output to Laser Disk (COLD) is an optical storage technology for transferring data to optical disk for near-online storage.

Control Data Set (CDS) is an SMS VSAM linear data set containing configurational, operational, or communication information. See SMS.

Control Data Set (CDS) is the DASD data set in which StorageTek's Host Software Component (HSC) maintains information on the cartridges stored in each automated cartridge system (ACS). See HSC.

Digital Lempel-Ziv (DLZ) is an improved form of the LZW data compression algorithm. See LZW.

Direct-Access Storage Device (DASD) is generic nomenclature for a storage peripheral that can respond directly to random requests for information; usually denotes a disk drive.

Enhanced Capacity Cartridge System Tape (ECCST) is a double length tape cartridge with a nominal uncompressed capacity of approximately 800 Mbytes.

Enhanced Cartridge Access Port (ECAP) is an 80-cartridge enter/eject facility for a StorageTek robotic tape library. See CAP.

Enterprise Systems Connection (ESCON) is IBM's fiber-optic technology for connecting mainframes using IBM channels. ESCON architecture provides fast access to disk arrays and tape. See FICON.

Exabyte is 1024 (or 1000) petabytes.

Fibre Channel (FC) is highly-reliable, gigabit interconnect technology allows concurrent communications among workstations, mainframes, servers, data storage systems, and other peripherals using SCSI and IP protocols.

Fibre Connectivity (FICON) is a fibre optic technology that provides higher speeds at longer distances than ESCON. See ESCON.

Giant MagnetoResistive Head (GMR) has great sensitivity to magnetic fields from the disk, making it possible to detect smaller recorded bits and to read these bits at higher data rates. See MRH.

Gigabyte (GB) is 1024 (or 1000) megabytes.

Hard Disk Drive (HDD), also called a Winchester drive, is a spinning magnetic disk accessed by a flying head.

Hardware Configuration Definition (HCD) is an interactive interface that enables an installation to define I/O configurations to both the software and hardware from one interface.

Head/Disk Assembly (HDA) is a sealed Winchester assembly, including disks, heads, filter and actuator assembly.

Hierarchical Storage Management (HSM) is software that automatically migrates unreferenced data sets from expensive, high-speed storage media, such as DASD, to progressively cheaper, less accessible media, such as tape.

Host Software Component (HSC) is the StorageTek software component that maintains, in a DASD control data set (CDS), records of the cartridges stored in each automated cartridge system (ACS). It routes mount/dismount messages to the library management unit (LMU).

Improved Cartridge Recording Capability (ICRC) is StorageTek's compression algorithm, that provides about 3:1 data compression on tape.

Improved Data Recording Capability (IDRC) is IBM's compression algorithm, that provides about 3:1 data compression on tape. Sometimes called Compact.

Interactive Storage Management Facility (ISMF) is the interactive interface of DFSMS/MVS that allows users and storage administrators access to storage management functions.

InterBlock Gap (IBG) is the space left unused between consecutive data blocks.

Input/Output Definition File (IODF) is where IBM stores hardware and software configurations.

Inputs/Outputs per second (IOPS) is a measure of performance for a host-attached storage device or RAID controller.

Just a Bunch Of Disks (JBOD) is a non-RAID disk array, where multiple disk drives are attached to an array bus, so that the host sees each drive as a separate volume.

Kilobyte (KB) is 1024 (or 1000) bytes.

Lempel-Ziv-Welch (LZW) is a data compression algorithm based on repeating strings. There are a number of variations, such as LZ1 and DLZ.

Library Control Unit (LCU) connects a StorageTek tape robotic unit to a Library Management Unit (LMU) and controls the robot movement.

Library Management Unit (LMU) is the StorageTek control path to the host, that can manage up to 16 robotic tape units.

Library Storage Module (LSM) is a tape library containing cells (or slots or bins) in which cartridges are stored, usually for access by an automated cartridge system. See ACS.

Linear Tape Open (LTO) is a new open tape architecture. LTO tapes are expected to surpass current tape capacity and performance benchmarks.

Magneto-Resistive Head (MRH) is a read head technology designed to support data acquisition from media with very high recording densities. See GMR.

Mean Swaps Between Failure (MSBF) is the average number of swaps a jukebox or tape library can be expected to deliver before maintenance is required.

Mean Time Between Failure (MTBF) is the average time before a failure can be expected to occur.

Mean Time until Data Loss (MTDL) is the average time until a component failure can be expected to cause data loss. This includes the consideration that RAID redundancy can protect against data loss from the failure of a single component.

Mean Time To Repair (MTTR) is the average time before an electronic component can be exepected to require repair.

Megabyte (MB) is 1024 (or 1000) kilobytes.

Multiple Volume Cartridge (MVC) is a "real" physical cartridge that contains multiple virtual volumes.

Nearline Control Solution (NCS) is an MVS-based StorageTek software product that supports more than 16 MVS images sharing a single library complex. It is designed specifically for use in parallel sysplex environments.

Non-Volatile Storage (NVS) is random access memory storage whose contents are not lost when power is removed.

Parallel Access Volume (PAV) is an IBM feature that allows multiple applications to access the same data at the same time.

Pass-Through-Port (PTP) allows cartridges to be passed between StorageTek robotic units.

Petabyte is 1024 (or 1000) terabytes.

Redundant Array of Independent (or Inexpensive) Disks (RAID) is a series of storage technologies involving large groups of small disk drives.

Redundant Array of Independent Libraries (RAIL) is for tape libraries what RAID is for DASD. See RAID.

Redundant Array of Independent Tape (RAIT) is for tapes what RAID is for DASD. See RAID.

ReMovable Media (RMM) is IBM's tape management software product.

Real Tape Drive (RTD) is a physical tape drive. See VTD.

Serial Storage Architecture (SSA) is an industry-standard interface that provides high-performance fault-tolerant attachment to I/O storage devices. See SCSI.

Silo is an alternative name for an Automated Cartridge System. See ACS.

Single Large Expensive Disk (SLED) means the mainframe hard disks that were used as a basis for comparison during the initial UC Berkeley RAID studies.

Small Computer Systems Interface (SCSI) is a standard, intelligent parallel interface for attaching peripheral devices to computers, based on a device independent protocol. See SSA.

Solid State Disk (SSD) is a high-speed, random-access storage peripheral.

Source Control Data Set (SCDS) is a VSAM linear data set containing an SMS configuration. See SMS.

Storage Area Network (SAN) is a centrally managed network that allows any-to-any interconnection of servers and storage systems.

Storage Management Subsystem (SMS) takes over many storage management tasks that were previously performed manually, such as such as space management, backup processing, and data set allocation.

Storage Resource Management (SRM) is the industry term for software that manages storage.

Tape Configuration Database (TCDB) is an ICF user catalog, which contains an inventory of the tape libraries and volumes in the libraries.

Tape Mount Management (TMM) is a method of reducing tape mounts by allowing the system to manage the placement of data.

A Tape Subsystem contains transports (or tape drives) controlled by a tape controller and attached to a host. The drives seen by the host may be real (physical) or they may be virtual (logical) drives emulated within the control unit.

Terabyte (TB) is 1024 (or 1000) gigabytes.

Tracks Per Inch (TPI) is the number of tracks written within an inch on a disk's surface: a measure of track density.

A Transport is the device into which a magnetic tape cartridge can be inserted in order to be accessible by the read/write heads and eject mechanism.

Unit Control Block (UCB) is a control block in storage that describes the characteristics of a particular I/O device on the operating system.

Virtual Storage Manager (VSM) controls StorageTek's virtual tape system. It consists of software and disk cache.

Virtual Tape Control System (VTCS) is the name of the host software component in StorageTek's Virtual Storage Manager (VSM).

Virtual Tape Drive (VTD) is an emulation of a physical transport in the virtual tape storage subsystem (VTSS) that looks like a physical tape transport to the host. The data written to the VTD is really being written to DASD. See VTSS.

Virtual Tape Servers (or Systems) (VTS) comprise: a robotic library to perform automated tape mounts for backend requirements; real tape transports that read and write virtual volumes from physical cartridges; a control database that cross-references logical to physical volumes; a DASD buffer that represents a tape to the system it is attached to.

Virtual Tape Storage Subsystem (VTSS) is a DASD buffer containing virtual tape volumes (VTV) and virtual tape drives (VTD). The VTSS is a StorageTek RAID 6 hardware device. See VTD and VTV.

Virtual Tape Volume (VTV) is a DASD buffer that appears to the operating system as a real tape volume. Data can be written to and read from the VTV, and the VTV can be migrated to and recalled from real tape. Mutliple VTVs can be written to one physical tape volume.

Vital Record Specifications (VRS) are RMM retention and movement policies for data sets and volumes. See RMM.

Volume Mount Analyzer (VMA) is an IBM utility that helps analyze the current tape environment.

Volume Table Of Contents (VTOC) is the data set on a DASD volume that specifies the location of all non-SMS data sets on that volume. See VVDS.

VSAM Volume Data Set (VVDS) is the part of the ICF catalog that resides on each DASD volume and contains information on the SMS-managed data sets on that volume. See VTOC.

VSAM Volume Data Set (VVDS) is a data set that describes the characteristics of VSAM and system-managed data sets residing on a given DASD volume; part of an integrated catalog facility (ICF) catalog.

Write Once Read Many (WORM) storage media are used for archival and secure data: usually refers to optical disk, but also to StorageTek's VolSafe tapes.

Yottabyte is 1024 (or 1000) zettabytes.

Zettabyte is 1024 (or 1000) exabytes.

Find more technical definitions in TechEncyclopedia.