IBM System/370 Manual page 47

Page of GC20-1 730-0
Revised 7/14/70
By TNL GN20-2227
r-40"-+ 60"
~
T
G E
C
A
60"
Control
Unit
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F D 8
1
3330 3330 3330 3330
3830
Figure 20.10.1. The 3330 facility
Facility configurations and maximum capacities, using full track
records, are shown below:
3830 Storage control + one 3330 module 200 megabytes
3830 Storage Control
+
two 3330 modules 400 megabytes
3830 Storage Control + three 3330 modules 600 megabytes
3830 Storage Control + four 3330 modules 800 megabytes
Drives are mounted in powered drawers that are opened and closed
by a switch on the operator control panel on the 3330 module. Logical
address plugs are supplied, as for the 2314, in addition to a CE service
plug. The latter is used when inline diagnostics are to be executed.
Functionally, the 3330 facility provides more capabilities than
the 2314, particularly in the areas of performance and availability.
The 3330 facility supports all the standard 2314 commands (except the
file scan commands) in addition to several new operations, including
RPS and error recovery commands. The 3330 facility also is an
attractive growth device for the 2321 Data Cell Drive.
The new" removable 3336 Disk Packs are interchangeable across 3330
disk drives but are not interchangeable with the 2316 Disk Packs used
on 2314 disk drives (Table 20.10.2 compares disk pack characteristics).
Like 2316 packs, 3336 Disk Packs will
be
initialized in the factory
with home addresses and capacity records (RO). Up to 20 defective
tracks per pack will be flagged and have alternates assigned. The
quick DASDI routine (part of the IEHDASDR utility) currently available
for processing 1316 and 2316 packs, will support 3336 packs. Quick
DASDI writes the volume label, the VTOC, and, if requested, IPL rec-
ords but bypasses track analysis. It also determines the number of
flagged tracks and places this data in the VTOC.
Table 20.10.1 compares the capacity and timing characteristics
of the 3330 facility with those of the 2314 facility and the 2321 Data
Cell Drive. The increase in capacity achieved
by
replacing a 2314
or a 2321 with a 3330 depends upon the block size chosen for the data
on the 3330. For example, if the 2314 full track block size of 7294
bytes is maintained for a given data set on the 3330 to avoid
programming changes, the 3330 yields a 91~ increase in full pack
capacity (almost twice the capacity). However, reblocking to a full
track on the 3330, 13,030 bytes, yields a 2421 full pack capacity
increase. If there is not enough processor storage available to
allocate I/O areas of 13,030 bytes, lowering the 3330 block size used
to half a 3330 track yields a 2391 increase in full pack capacity.
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