User Guide

Ampex 1308911-02 A-1
Glossary and Acronyms Glossary
Appendix A
Glossary and Acronyms
A.1 Glossary
Absolute Double Frame Number (ADFN)
The basic unit of data storage on a DD-2 tape. There is a unique,
unsigned 24-bit numerical identifier for each double frame (physical
block) on a formatted tape. ADFN increments by one for each
successive double frame, including those containing only system
information as well as those that can accept user data. Helical
recording begins at ADFN 2048. ADFN locations may be of use when
doing complex positioning operations on a DD-2 tape.
Alternate Partition Layout
A tape format that alternates partitions and system zones. No system
zones occur within any partition, and each partition is followed
immediately by a system zone. See also Pack, Stretch, and Waste
partition layouts.
Append-Only An interface parameter that allows data to be written to the tape only
at the EOD position, providing a certain level of protection against
overwriting existing data.
Beginning of Media (BOM)
The 25 physical blocks (approximately 28.6 MB) prior to the
beginning of each partition used by the DST drive to synchronize
electronics to the data recorded on tape. This area is not available for
user data.
Beginning of Partition (BOP)
A mark recorded on the Logical Address Track that indicates the start
of a user data partition.
Beginning of Tape Zone (BOT)
A zone near the beginning of tape used, like any system zone, for
physically threading and unthreading tape around DST tape drive read/
write heads. The BOT zone starts at the physical beginning of tape
(PBOT) and ends at the physical beginning of media (PBOM). See
System Zone.
Block The smallest unit in which data can be transferred over a blocked
interface. See Data Block and Physical Block.