3270 User Connects to Host Session of Previous User (175336)

SYMPTOMS

When using pooled 3270 LUs with SNA Server, a new 3270 user connects to the host session of the previous user. This problem was observed when using a CICS host application, and CICS and VTAM are configured to use the CLSDST and OPTION=PASS host options.

When CICS issues CLSDST, it saves information about the user id and LU. The CLSDST=PASS option causes VTAM to drop the current session, put in on queue, and then start a new session with another VTAM application. When the second session ends, VTAM takes the session on the queue, and then establishes a session between the LU and CICS. CICS retrieves the saved information about the user id, so the users do not need to do a new sign on to RACF.

CAUSE

When SNA Server terminates a 3270 session, SNA Server sends a TERMSELF to the host, followed by NOTIFY with type 01, which means:

SLU capability is disabled. Sessions can be Queued but not started.

When a new user activates a 3270 session, SNA Server sends a NOTIFY(type 03 = SLU Enabled), the old CICS session is started over the LU.

This problem does not occur if SNA Server sends a NOTIFY Type 00, which means

SLU Capability is Inhibited. Sessions can be Neither Queued nor Started.

STATUS

Microsoft has confirmed this to be a problem in SNA Server versions listed at the beginning of this article.

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

An update to SNA Server 3.0 Service Pack 2 is available from Microsoft which supports the ability to send a NOTIFY with type = 00 (SLU Inhibited) when a 3270 session is ended. With this update applied, the following registry entry can be used to activate this behavior:

   HKEY_LOCAL_MACHINE/System/CurrentControlSet/Services/Snaservr
   /parameters/ 

   NotifyInhibited: REG_SZ: YES

Note: This registry parameter is also available in SNA Server 4.0.

For additional information about SNA Server 3270 session termination, please see the following article in the Microsoft Knowledge Base:

132436 SNA Server Handling of 3270 LU Session Cleanup