Common questions

These common questions are typically associated with BARR/CHANNEL. If you can't find the answer to your question here, click the Index or Search tab of the Help to search for a specific word or phrase.

How do I optimize the SNA gateway with BARR/CHANNEL link service?

Safely turning off and turning on a computer running BARR/CHANNEL and the attached CAB

Follow these steps to safely turn off and turn on the computer.

To turn off the equipment

Stop the PUs in VTAM that are controlled by the SNA gateway.
Turn off the computer running SNA Server or HIS.
Turn off the CAB.

To turn on the equipment

Restart the PUs in VTAM.
Turn on the computer running SNA Server or HIS.
Turn on the CAB.

Installing multiple channel adapters in the same computer

Most computers will only support three PCI cards, while some newer computers can support four or more. So, the number of channel adapters you can install is mostly dependant on your computer, and the number of PCI-style cards (video card, network card, etc.) that are installed.

If you are attempting to set up a server with a large number of connections and sessions, be sure your computer has sufficient RAM (64-128MB) and a fast hard drive.

For load balancing purposes, you may want to install more than one adapter and divide the connections (sessions) between the adapters.

Determining the maximum number of sessions and connections supported by SNA Manager

This information was taken from the Microsoft SNA Server Help, under the Adapter, Connection, and Server Capacities for SNA Server topic:

SNA Server (version 3.0 or 4.0) and HIS support the following maximum (theoretical) capacities.

15,000 sessions per server
250 total connections per server
Maximum of 5,000 clients per server (one downstream connection is equivalent to one client when figuring the total number of clients per server)

The following table gives the upper limits for connections and sessions.

Connection	Maximum connections per adapter	Maximum sessions per connection
802.2	250	254
SDLC	1	254
X.25	250	254
DFT	1	5
Channel	250	254
Twinax	1	20

Based on the above table, a channel adapter can support a maximum of 250 connections per adapter, and a maximum of 254 sessions per connection (for a theoretical maximum of 63,500 sessions per adapter). An SDLC card, by comparison, can only support 1 connection per adapter, for a maximum of 254 sessions. Microsoft's Technet Web site contains the following additional information from the SNA Server (version 4.0) release notes:

The maximum number of 802.2 Link Services that one SNA Server computer can support is:

64 per network adapter (limited by SAP)
255 per SNA Server computer (limited by index from 0x01 to 0xFF)