beginning of tape. It means that policy is determined
on writes at LB (logical block) zero (the first block in
the partition). Appending to a tape [or overwriting at a
non-zero LB] does not change the policy already in use
for that tape.
Border Gateway Protocol (BGP). BGP is the core
routing protocol of the Internet. It works by
maintaining a table of IP networks or ’prefixes’ which
designate network reachability among autonomous
systems (AS).
browser. A client program that initiates requests to a
Web server and displays the information that the server
returns.
buffer. A routine or storage used to compensate for a
difference in rate of flow of data or time of occurrence
of events, when transferring data from one device to
another.
bus. A facility for transferring data between several
devices located between two end points, only one
device being able to transmit at a given moment.
byte. A string consisting of a certain number of bits
(usually 8) that are treated as a unit and represent a
character. A fundamental data unit.
C
capacity. The amount of data that can be contained on
storage media and expressed in bytes of data.
cartridge storage slot. Individual slot located within a
magazine that is used to house tape cartridges.
caution (notice). A word to call attention to possible
personal harm to people. Contrast with attention and
danger.
centimeter (cm). One one-hundredth of a meter (0.01
m). Approximately 0.39 inch.
channel command. An instruction that directs a data
channel, control unit, or device to perform an operation
or set of operations.
char. Character.
CHK. Check.
cleaning cartridge. A tape cartridge that is used to
clean the heads of a tape drive. Contrast with data
cartridge.
command. A control signal that initiates an action or
the start of a sequence of actions.
compact disc (CD). A disc, usually 4.75 inches in
diameter, from which data is read optically by means of
a laser.
compression. The process of eliminating gaps, empty
fields, redundancies, and unnecessary data to shorten
the length of records or blocks.
concurrent. Refers to diagnostic procedures that can
be run on one control unit while the rest of the
subsystem remains available for customer applications.
contingent connection. A connection between a
channel path and a drive caused when a unit check
occurs during an I/O operation.
controller. A device that provides the interface
between a system and one or more tape drives.
control path drive. A drive that communicates
messages from the host computer to the library in
which the drive is installed.
CP. Circuit protector.
ctrl. Control.
CU. Control unit.
D
danger (notice). A word to call attention to possible
lethal harm to people. Contrast with attention and
caution.
data. Any representations such as characters or analog
quantities to which meaning is or might be assigned.
data buffer. The storage buffer in the control unit.
This buffer is used to increase the data transfer rate
between the control unit and the channel.
data cartridge. A tape cartridge dedicated to storing
data. Contrast with cleaning cartridge.
data check. A synchronous or asynchronous indication
of a condition caused by invalid data or incorrect
positioning of data.
dc. Direct current.
DCS. Designated Cleaning Slot
degauss. To make a magnetic tape nonmagnetic by
means of electrical coils carrying currents that
neutralize the magnetism of the tape.
degausser. A device that makes magnetic tape
nonmagnetic.
degradation. A decrease in quality of output or
throughput or an increase in machine error rate.
degraded. Decreased in quality of output or
throughput or increased machine error rate.
Density reporting. This setting determines whether
the drive shows or masks encryption. This settings
H-2 Dell PowerVault TL2000 Tape Library and TL4000 Tape Library User's Guide
