Black Box KV162A manual Independent vs. shared access in a multiuser system

CHAPTER 8: Operation

Of course, any time that more than the maximum independent number of users are trying to access computers attached to a single ServSwitch Multi unit, two, four, or eight of them will have independent access and the rest must share. Any attempt by a sharing user to connect to a third/fifth/ninth computer attached to the same Switch will be ignored. Figure 8-1 below shows a “mandatory sharing” system with five consoles. The users on consoles 3, 4, and 5 are using computers B through D respectively. They are working simultaneously and independently of each other. Consoles 1 and 2 are sharing computer A. Both consoles display video from computer A, but only one of the consoles can have actual control of the computer at any given moment.

Computer D Computer C Computer B Computer A

		Com. A	SHARED
			ACCESS
		Video
		Console 1
Com. D	Com. C	Com. B	Com. A
Video	Video	Video	Video
Console 5	Console 4	Console 3	Console 2
	INDEPENDENT ACCESS

Figure 8-1. Independent vs. shared access in a multiuser system.

In cascaded systems, the situation becomes more complicated. Each individual ServSwitch Multi still has two, four, or eight data pathways, but when a user selects a computer on another Switch, one pathway in each Switch between the user’s console and the computer will be occupied. For example, refer to Figure 6-4 in Section 6.1:

For a user on Switch 0 to establish an independent connection to a computer on Switch 5, it would require the use of one data pathway in Switch 5 (from the CPU-Interface Card to the Transmit-Card port), one pathway in Switch 4 (from Receive-Card port to Transmit-Card port), one in Switch 1 (Receive-Card port to Transmit-Card port), and one in Switch 0 (Receive-Card port to local console or User-Interface Card).

When you need to figure out the dynamics of data-path usage in any local ServSwitch Multi in a cascaded ServSwitch Multi system, just remember that each of these connections takes up one data path through the unit:

•Local console to local computer.

•Local console to remote computer through a port on a local Receive Card.

•Remote console to local computer through a port on a local Transmit Card.

•Remote console to remote computer through ports on local Transmit and Receive Cards.

In cascaded systems, shared access applies not only to computers but also to expansion connections. If one ServSwitch Multi is attached to another by only a single link (from a Transmit-Card port on one Switch to a Receive-Card port on the other), and an active user at a console on the Switch with the Receive Card selects a computer on the Switch with the Transmit Card, other users on the Receive-Card switch can share access to that computer, but they cannot establish an independent connection to any computer on the Transmit-Card Switch until the active user selects a computer on a different Switch and relinquishes his or her “lock” on the expansion connection.

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