Perfmon Degrades SNA Server When Many 3270 LUs in Use

• Microsoft SNA Server for Windows NT, versions 2.11 (all SP), 3.0 (all SP), 4.0

SYMPTOMS

When you use Windows NT Performance Monitor to monitor any SNA performance objects every second, SNA Server performance degrades significantly when 150 users or more have an active 3270 session. Users with active 3270 sessions receive host response delays from 20 seconds to two minutes.

CAUSE

When you monitor SNA Server performance objects, SNA Server reports response time monitor (RTM) performance data on every active 3270 LU. When a large number of 3270 LUs are in use, this reporting can degrade 3270 performance for current 3270 users if a small Performance Monitor reporting interval is chosen (such as the default one-second reporting interval in Windows NT Performance Monitor).

RESOLUTION

To prevent the problem from occurring with SNA Server 2.11 or 3.0, follow these steps:

1. Choose an infrequent Performance Monitor reporting interval, such as one minute or more, rather than the default of one second.



2. Do not continuously monitor SNA Server performance objects during production use

STATUS

Microsoft has confirmed this behavior with SNA Server versions 2.11, 3.0, and 4.0 and is investigating how to address this issue in future releases.

This problem was corrected in the latest SNA Server version 4.0 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

<snaroot>\system\snaservr.exe
<snaroot>\system\trcservr.exe
<snaroot>\system\snaperf.dll

MORE INFORMATION

For additional information about another possible performance problem, please see the following article in the Microsoft Knowledge Base:

Q168717 SNA Server Performance Degrades If Domain Controller Down

Additional query words:

Keywords : kbnetwork kbbug4.00 kbfix4.00.sp1 kbbug3.00 kbbug2.11 snaserverservice
Version : winnt:2.11 (all SP),3.0 (all SP),4.0
Platform : winnt
Issue type : kbbug