IBM System/370 Guide

Page of GC20-1730-0
Added 11/20/70
By TNL GN20-2277
The 3803 also contains diagnostics that are operative during normal
tape processing operations. These diagnostics perform operations such
as the monitoring of measurement functions of the tape units. If an
irregularity is noted, the control unit generates sense bits to inform
the executing program of the malfunction.
Tape subsystem availability is improved by radial attachment of
3420 tape units to the 3803 control unit. That is, each 3420 is cabled
directly to the control unit so that any malfunctioning tape unit can
be disconnected from the tape subsystem for servicing without disturbing
the other tape units. When tape units are attached to the control
unit in series (each tape unit cabled to the next tape unit), as are
2400-series units, the entire tape subsystem must be taken offline
to uncable a tape unit.
These new features, combined with the use of fewer adjustable parts,
are designed to provide optimum tape subsystem availability through
better reliability and reduced maintenance time.
In conclusion, the 3803/3420 Magnetic Tape Subsystem offers Model
65 and 75 tape unit users the following:
• Fast data rates, fast access times, and faster rewind time for
short files than on 2401 tape units. In-flight correction of
single-bit read errors eliminates a backspace and reread procedure
and reduces the number of permanent read errors.
• Automatic tape threading and cartridge loading to reduce tape setup
tiIl1e
•
1600-BPI density to reduce the tape volume requirements for
multivolume data files recorded at lower densities
• Less tape media wear as a result of the transport design and
automatic threading and less tape damage caused by handling if
wraparound cartridges are used for tape volume mounting and storage
• Reduced maintenance time because of the transport design (fewer
adjustable parts), functional packaging of components, expanded
sense bytes, and microdiagnostics resident in the control unit
• Increased tape subsystem availability because of reduced maintenance
requirements
• Compatibility with existing 2400-series tape volumes and programs
These advantages, combined with lower subsystem cost and compact,
flexible tape-switching capability, make the 3803/3420 Magnetic Tape
Subsystem the natural growth path for tape users.
51.8

IBM System/370 Specifications

General

Brand	IBM
Model	System/370
Category	Server
Language	English