StorageTek 6 How Communications Services are Set or Changed, Host Software Component Functions

How Communications Services are Set or Changed

Communications services are set or changed by the Communications Path (COMMPath) command and control statement. This command specifies host, communication method, LMU paths and VTAM path name for the associated host. The communication path definitions can be modified at any time during library operation without terminating the HSC.

The COMMPath command and control statement sets up a table of definitions for the host that is executing the command. Each host’s table must contain a list of path definitions for itself and a separate list for each defined host. Therefore, on each host, the command must be issued once to define the paths for itself, once to define the paths for a second host, once to define the paths for a third host, and so on, until all hosts are defined.

For example, the library is operating in an environment with three hosts: Host 0, Host 1, and Host 2. The COMMPath command must be issued three times on each host. The table of definitions for Host0 must contain a list of paths for Host 0, a list for Host 1, and a list for Host 2. The same is true for Host 1 and Host 2.

For one host to communicate with another, they must have matching entries in their respective lists of defined paths. The highest-performance method that is common to two hosts is selected as the current method of communications between the two. A host can use one method of communications with a second host, and a different method of communications with a third host.

Figure 9 illustrates how different communication methods can be used between multiple hosts.

	HOST 0	VTAM		HOST 2
	METHODS	COMMUNICATIONS		METHODS
	VTAM			VTAM
	CDS			LMU
				CDS
	CDS			LMU
COMMUNICATIONS			COMMUNICATIONS

HOST 1

METHODS

LMU

CDS

EACH PAIR OF HOSTS COMMUNICATE USING THE

HIGHEST PERFORMANCE METHOD DEFINED TO BOTH C26184

Figure 8. HSC Communication Methods Between Multiple Hosts

Chapter 2. Host Software Component Functions 79

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