Hardware Features Of 3330 And 2314 Facilities; 20:15 The 2305 Fixed Head Storage Module And 2835 Storage Control Models 1 And - IBM System/370 Manual

and ease of engineering change installation. These factors add to
the improvement of total system availability.
Table 20.10.3. Hardware features of 3330 and 2314 facilities
Feature
3330
2314
Number of drives per
facility
2,. 4, 6, or 8 1, 2" 3. 4 , 5. 6, 1,
or 8 (A ninth can
be
included as a spare
only. )
Removable interchangeable
disk packs
Removable address plugs
Record overflow feature
File scan feature
Multiple track operations
Two-channel switch
Second control unit
(to permit two concurrent
data transfer operations
on a facility)
Rotational position sensing
Multiple requesting
Command retry by control
unit and channel
Error correction data
presented by control unit
writable storage in
control unit loaded from a
magnetic disk cartridge
Inline diagnostic tests
initiated via the CE
panel in the facility
Inline diagnostic tests
initiated via the system
console
Yes
Yes
Standard
Not available
Standard
Optional
Not available
Standard
(128 sectors/track)
The control unit
can concurrently
handle one channel
program on each
of its drives.
Standard
Yes
Yes
Standard
Standard
Yes
Yes
Standard
Standard
Standard
Optional
Optional (2844
Auxiliary Storage
Control)
Not available
Not available
Not implemented
No
No
Standard
Not implemented
20: 15 THE 2305 FIXED HEAD STORAGE MODULE AND 2835 STORAGE CONTROL
MODELS
1.
AND
1
One or two 2305 Fixed Head Storage Modules can be attached to a
2835 Storage Control unit. Each module contains six nonremovable
rotating disks on which data is recorded. Read/write heads, called
recording elements, are fixed in position to access each track on the
twelve recording surfaces so that no arm motion is required. (See
Table 20.15.3 at the end of this subsection for a comparison of the
characteristics of the 2305, Models 1 and 2, with those of 2301 Drum
Storage. )
Spare, or alternate, tracks are provided in 2305 modules and must
be wired in by a customer engineer to replace defective recording
tracks. However, one spare track is available for assignment by the
alternate track assignment utility program when a permanent track error
occurs on a recording track during processing. Once a spare has been
assigned as an alternate track, the hardware automatically accesses
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