Specifications

ATAPI For Streaming Tape QIC-157 Rev B
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Some multi-track Devices have only one track group, using a parallel storage format that supports the
simultaneous recording of all available tracks.
The serpentine and parallel recording formats define tracks as longitudinal patterns of recorded
information.
For most recording formats, an area at beginning-of-medium contains a format identification as a
tone burst or some other recognizable pattern. User data is not recorded in this area. The format
identification is an attribute of a volume used for interchange purposes and is defined in applicable
standards.
5.1.1. Early Warning
When writing, the Host needs an indication that it is approaching the end of the permissible recording
area. This position, called early-warning (EW), is typically reported to the Host at a position early
enough for the Device to write any buffered data to the medium while still leaving enough room for
additional recorded labels or filemarks. Some American National Standards include physical
requirements for a marker placed on the medium to be detected by the Device as early-warning.
For Devices that implement large data buffers, the early-warning position defined by a physical
marker may be too close to the end of the recording region to permit emptying the data buffer(s). For
these Devices, a logical concept of early-warning shall be used to signal the Host at an appropriate
location prior to the physical marker.
5.1.2. Partitions
Another attribute of a volume is called a partition. Partitions consist of one or more non-overlapped
mini-volumes, each with its own beginning and ending points, occupying a single physical volume.
Each partition (x) within a volume has a defined beginning-of-partition (BOPx), an early-warning
position (EWx), and an end-of-partition (EOPx).
All volumes have a minimum of one partition called partition zero, the default data partition. For
Devices that support only one partition, the beginning-of-partition zero (BOP0) may be equivalent to
the beginning-of-medium and the end-of-partition zero (EOP0) may be equivalent to the end-of-
medium.
When a volume is mounted, it is logically positioned to beginning of the default data partition
(BOP0). When a REWIND command is received in any partition (x), the Device positions to the
beginning-of-partition (BOPx).
Partitions on a volume do not need to be recorded in any defined order, nor do all partition numbers in
a sequence need to be present on a volume. It is sufficient for a Device to be able to locate a partition,
given its code value, or determine that it does not exist on the volume. For interchange, information
about which partitions are present on a volume may be stored on the volume in a Device-defined area
(possibly unavailable to the Host) or the information may be an intrinsic attribute of the Device
implementation.
5.2. Quick File Access
Partitions MUST start on track boundaries at the physical BOT end of the tape. Partitions shall be
used to support the implementation of QFA (Quick File Access). QFA is a feature that provides
support for two partitions on the tape cartridge, a directory partition and a data partition. For this
specification, the partitions are defined by the Device.