Disaster Recovery Plan
Mainframe Equipment I/O Cabling
Last update: Tuesday, 21-Mar-2000 10:34:54 CST
This document contains the detailed specifications for the
mainframe I/O channel cable connections in the
Several precautions are to be observed when making the
channel cable connections:
- Avoid static electricity discharges directly into a channel cable
connector's pins. Hitachi Data Systems requires the use of a static
electricity wrist wrap when connecting cables to the HDS mainframe or any
device connected to the HDS mainframe.
- Examine the pins on a connector beforehand for any bent pins. Most
bent pins can be repaired by carefully straightening it out. If a pin is
smashed too far into the connector or is broken, discard the entire cable.
- Use care when mating a channel cable connector into the socket on the
computer device. Do not force the connector. Avoid bending connector
- Channel cables come in bus and tag cable pairs. The two cables are
identical, but you must ensure that the two are not crossed over and that
the two cables are of the same length. The bus output port on a device
must always connect to the bus input port on the next device. In similar
fashion, the tag output port on a device must always connect to the tag
input port on the next device.
- Polarity of channel cables is critical. The connectors on the ends of
the cable are color coded. Typically, the very end of one is all black
and the other end is gray (some may be white). The black ends always
attaches to a bus or tag OUTPUT port on a device. The gray end always
attaches to a bus or tag INPUT port on a device. An easy to remember
mnemonic is "GRAY AWAY", meaning that the gray end is always furthest away
from the CPU.
- The last device on a channel must always be terminated. Channel
terminators come in bus and tag pairs. The bus output port of the last
device must always be terminated with a bus terminator, and the tag output
port of the last device must always be terminated with a tag terminator.
Take the same precautions when connecting a terminator as a channel cable
connector to ensure that a proper connection is made and that no pins are
bent in the process.
- The following diagram illustrates the proper orientation and termination
of parallel channel cables:
DRPHDS02: Parallel Channel Cable Attachment Diagram
look into the end of an ESCON fiber optic cable.
The bright light source from a connected cable may cause
LOSS OF EYESIGHT or PARTIAL BLINDNESS.
Channel Cable Lengths
Because of the cramped conditions in the Cold Site, and because there is
no raised floor, it will be important that channel cables be ordered that
are very close to being the correct lengths necessary. Otherwise, excess
cable must be coiled and will pose a problem for installation and repair
personnel needing access to the equipment.
Cable Layouts and Equipment Egresses
Because there is no raised floor in the Cold Site, channel cables will
extend between devices across the floor. This can pose a difficult
problem when it becomes necessary to move a piece of equipment after the
cables have been connected. For this reason the layout of the channel
cables in the Cold Site has been planned to provide egress paths for
moving equipment around.
Power cables pose the same problem, so the electricians must be sure to
follow the guidelines published within this plan to provide power cables
of the proper lengths. The layout of power cables has also been planned
to provide egress paths for moving equipment.
||W A R N I N G
Avoid stepping on channel and power cables or moving them during normal
system operation. Doing so may result in system or device failures. It
is highly recommended that the entire machine room area, except for the
area where the operator consoles are manned, be posted as off limits to
reduce the risk that system damage or failure will occur.
Channel Layout Specifications
The following documents contain the detailed specifications for the
channel cable connections and layout.
DRPMS105: Mainframe Channel Cable Connections
DRPMS106: Mainframe Channel and Power Cable Layout
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