SNA Server PU/LU Reactivation Fails After VTAM Z NET CANCEL

ID: Q176768

The information in this article applies to:

Microsoft SNA Server, versions 3.0, 3.0 SP1, 3.0 SP2

SYMPTOMS

When Microsoft SNA Server is configured with one or more channel connections over the Polaris Escon channel adapter, not all of the PUs and LUs reactivate if VTAM is shut down quickly using the VTAM command:

z net, cancel

If VTAM is shut down in an orderly manner, the PUs and LUs do reactivate properly.

This problem was observed when SNA Server was configured with 15 PUs and 250 LUs each (3750 total LUs). Some LUs failed to reactivate when VTAM was restarted.

CAUSE

There are two different problems contributing to the reactivation problems:

SNA Server is not efficiently processing a large number of DACTLU messages from the host, causing slow performance in responding to DACTLU requests. This may cause the host to experience channel timeout errors during LU deactivation. This problem was fixed in SNA Server 3.0 Service Pack 2 (SP2), though was not listed in the 3.0 SP2 fix list Help file.

The Polaris link service is not responding quickly to SNA Server Close(Link) requests, causing the host to experience channel errors when attempting to reactivate the PUs and LUs when the host was brought back up again.

WORKAROUND

To work around this problem, do one of the following:

Stop VTAM using an orderly shutdown method, instead of using the "z net, cancel" option.

-OR-

Try disabling the channel PUs first
v net, id=xxxx,inact,f
before issuing the "z net, cancel ..." command.

STATUS

Microsoft has confirmed this to be a problem in the SNA Server version 3.0, 3.0 Service Pack 1 (SP1) and 3.0 SP2.

This problem was corrected in the latest SNA Server version 3.0 U.S. Service Pack. For information on obtaining this Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

S E R V P A C K

MORE INFORMATION

With this fix applied, SNA Server 3.0 was successfully tested with 15,000 LUs (the maximum LU capacity supported by SNA Server 3.0) over a single Polaris ESCON adapter (60 PUs, each with 250 LUs).

The fix described in the following Microsoft Knowledge Base article should also be applied when using SNA Server with thousands of 3270 or LUA LUs:

Q176020 SNA Server Starts Slowly When Configured with 15000 3270 LUs

Additional query words: znet barr

Keywords : kbnetwork prodsna kbbug3.00 kbfix3.00.sp3 snachannel snaserverservice
Version : WINDOWS:3.0,3.0 SP1,3.0 SP2
Platform : WINDOWS
Issue type : kbbug