DRPMS104: Mainframe Equipment I/O Cabling

Disaster Recovery Plan
Mainframe Equipment I/O Cabling
(DRPMS104)

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 BELL 108 Cold Site.

Precautions

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 pins.
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
NEVER 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