StorageTek 6 manual Switching Communications Paths

COMMPath can be specified by an operator as an operator command, or by a systems programmer as a PARMLIB control statement. Before COMMPath is issued, all methods of communications are set to CDS. Refer to ‘‘Communications Path (COMMPath) Command and Control Statement’’ in the HSC Operator’s Guide for information on the usage of the command.

It is recommended that host-to-host communications be defined in PARMLIB at startup. The COMMPath operator command is best used to switch communications paths, or to delete paths.

Displaying Current Status of Communication Services

The current status of the communications method is displayed by issuing the Display operator command. Issuing the Display command, specifying the COMMPath parameter, and optional HOSTid parameter results in a summary display at the console.

When issuing the command, individual hostids or all hosts can be specified. If you exclude the HOSTid parameter in the command, a summary of current parameter settings for all hosts is displayed in a message. If the HOSTid is specified as ‘‘*’’ the current settings are displayed for the host from which the command is entered. If the ALL parameter is issued, the current settings for all defined hosts are displayed.

The message provides a summary list for the current HSC host-to-host communications parameters.

Switching Communications Paths

The performance ranking of the communications methods takes on meaning when it becomes necessary to switch from one method to another because of a failure. A switch can be initiated automatically by the HSC or dynamically by the operator using the COMMPath command. The HSC issues a message to the console when a communications path switch occurs, regardless of how it is initiated.

The HSC can initiate

•a lateral switch from one defined LMU path to another, or

•a downward switch from a higher performance method to any lower performance method (VTAM to LMU, LMU to CDS, or VTAM to CDS).

The COMMPath command can initiate a switch to a higher, lower, or equivalent method.

Note: After an automatic downward switch has occurred, an upward switch can only be accomplished using the COMMPath command.

80VM/HSC 6.0 System Programmer’s Guide

1st ed., 6/30/04 - 312579601