Product manual

77 A1 69UP Rev00 G-1
Glossary
This glossary contains terms related to disk storage subsystems. Many of these
terms are used in this manual.
A
Actuator
A set of access arms and their attached read/write heads, which move as an independent component
within a head and disk assembly (HDA).
Adapter
Card that provides the physical interface between the director and disk devices (dual-initiator
adapter), director and parallel channels (Bus & Tag adapter), director, serial channels (serial
adapter), and SCSI host channels (SCSI adapter).
ADT
Automatic Diagnostic Test.
Alternate Track
A track designated to contain data in place of a defective primary track. See also Primary Track.
ANSI
American National Standards Institute. A standards-setting, non-government organization which
develops and publishes standards for voluntary use in the USA.
Asynchronous Transmission
A handshaking protocol that requires each byte be requested and acknowledged before the
transmission of the next byte begins.