IBM 201 manual ESD see electrostatic discharge ESM see environmental service monitor

engine. The unit that contains the processors that respond to requests for data from clients. This is where the operating software for the TotalStorage Model 200 appliance resides.

equivalent paths. A collection of paths to the storage device. The paths have no switchover time penalty when changing from one path group to another while accessing the storage device.

error. A discrepancy between a computed, observed, or measured value or condition and the true, specified, or theoretically correct value or condition (A) (I).

ESD (see electrostatic discharge).

ESM (see environmental service monitor).

Ethernet. A standard protocol for a 10-Mbps baseband local area network (LAN) that allows multiple access and handles contention by using Carrier Sense Multiple Access with Collision Detection (CSMA/CD) as the access method.

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

event message. Synonym for call-progress event message.

executable statement. A statement that specifies one or more actions to be taken by a computer program at execution time; for example, instructions for calculations to be performed, conditions to be tested, flow of control to be altered (T).

expansion slot. In personal-computer systems, one of several receptacles in the rear panel of the system unit into which a user can install an adapter.

extended configuration services. Configuration services that reside outside a CP processor. Extended configuration services keeps a local cache of transmission group locations. Extended configuration services do not handle activation and deactivation. See configuration services.

Extended Industry Standard Architecture (EISA). The PC bus standard that extends the AT bus (ISA bus) to 32 bits and provides busmastering. It was announced in 1988 as a 32-bit alternative to the Micro Channel that would preserve investment in existing boards. PC and AT cards (ISA cards) can plug into an EISA bus.

F

failback. The restoration of the appliance to its initial configuration after detection and repair of a failed network or appliance component.

failover. (1) The automatic recovery of resources in the event of a network outage, or failure of the hardware or software. (2) A cluster event where the primary database server or application server switches over to a backup system due to the failure of the primary server.

failover group. A type of virtual network interface. It is a collection of physical and bonded interfaces that provide backup for each other. Each member of the failover group must have the same front-end and backend connectivity.

failure. (1) The termination of the ability of a functional unit to perform its required function. (2) An uncorrected hardware error. Failures are either recoverable or not recoverable by the software or the operator. The operator is always notified when failures occur. Contrast with error.

Fast Ethernet. An Ethernet standard that provides a data rate of 100 Mbps.

feature code. A code used by IBM to process hardware and software orders.

Federal Communications Commission (FCC). A board of commissioners appointed by the President under the Communications Act of 1934, having the power to regulate all interstate and foreign communications by wire and radio originating in the United States.

fiber optic cable (see optical cable).

Fiber Optic Inter-Repeater Link (FOIRL). An IEEE standard for fiber optic Ethernet.

IBM Glossary of Storage Networking Terms 113