Microsoft KB Archive/240762

= Password Synch Fails after Promoting Backup SNAPMP Service =

Article ID: 240762

Article Last Modified on 6/24/2004

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APPLIES TO


 * Microsoft SNA Server 3.0 Service Pack 4
 * Microsoft SNA Server 4.0
 * Microsoft SNA Server 3.0 Service Pack 2
 * Microsoft SNA Server 3.0 Service Pack 3
 * Microsoft SNA Server 3.0 Service Pack 4
 * Microsoft SNA Server 4.0
 * Microsoft SNA Server 4.0 Service Pack 1
 * Microsoft SNA Server 4.0 Service Pack 2
 * Microsoft SNA Server 4.0 Service Pack 3

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This article was previously published under Q240762



SYMPTOMS
Changing a Windows NT password in an accounts domain (for example a Windows NT domain that contains user accounts) that is configured to replicate (or synchronize) password changes with a host (for example a mainframe or AS/400) using the SNA Server's Host Security Integration feature may fail. The PDC in the accounts domain logs the following event in the Windows NT application event log for each password change that cannot be replicated:

Event ID: 671

Source: SNA Host Security

Description: Password Change DLL was unable to send the RPC message. Error: STI - RpcSendConnection could not find an alternate server resource to send the rpc message to.

When this occurs, the user's Windows NT password is successfully changed; however, the new password is not propagated to the host system. The user receives an error indicating an invalid user name or password the next time they try to log on to the host system using the SNA Server Single Sign-On (SSO) feature.

Note: This only occurs when a Master or Multiple Master Domain model is used with the SNA Server Host Security components. In these environments, the PDCs of the accounts domains have the SNA Windows NT Account Synchronization (SNAPMP) service installed in a secondary (or backup) role.



CAUSE
The Password Change DLL (Snapwchg.dll) does not attempt to locate a new master (or primary) SNAPMP service in the Windows NT domain that contains the Host Security Domain if the original master SNAPMP service is no longer available. This only occurs if the master SNAPMP service is running in a Windows NT domain other than the one where the Password Change DLL exists.



RESOLUTION
To resolve this problem, obtain the latest service pack for SNA Server 4.0. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

215838 How to Obtain the Latest SNA Server Version 4.0 Service Pack



WORKAROUND
Restarting the PDCs in the accounts domains re-initializes the Password Change DLL, which allows it to locate the new master SNAPMP service in the Host Security Domain.



STATUS
Microsoft has confirmed that this is a problem in Microsoft SNA Server versions 3.0, 3.0 SP1, 3.0 SP2, 3.0 SP3, 3.0 SP4, 4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3.

This problem was first corrected in SNA Server 4.0 Service Pack 4.



MORE INFORMATION
In a master (or multiple master) domain topology that uses the SNA Server Host Security components, the typical configuration includes a resource domain that contains the SNA Server computers and the Host Security Domain that is defined to handle the user ID/password mapping and/or replication to the host system.

In this environment, the master SNAPMP service is installed on the PDC of the resource domain as is the SNA Host Account Cache (snadatabase) service. Secondary (or backup) instances of these services are typically installed on one or more BDCs in the resource domain. The SNAPMP service will only start on a PDC, so the secondary SNAPMP services do not actually start on the BDCs.

The SNAPMP service also needs to be installed in a secondary role on the PDCs of the accounts domains that will be participating in the Host Security Domain. The SNAPMP service does not start on these PDCs as it is configured in a secondary role. However, the Password Change DLL is initialized on these PDCs to detect any Windows NT password changes for users that are members of the Host Security Domain. The Password Change DLL intercepts the password change requests and then attempts to forward them to the master SNAPMP service so that they can be replicated to the host system, if the user is configured for password replication.

If the PDC with the master SNAPMP service becomes unavailable for any reason, a BDC can be promoted to PDC and then the SNAPMP service on this newly promoted PDC can be started as the "new" master SNAPMP for the Host Security Domain.

The problem described here occurs when a BDC in the resource domain is promoted to PDC and the SNAPMP service is started as the new master. The Password Change DLL in the accounts domain does not attempt to locate the new master SNAPMP once it fails to connect to the original master SNAPMP service.

Note: This does not occur if the user accounts exist in the same Windows NT domain as the master SNAPMP service, because the Password Change DLL is able to locate a new master SNAPMP service when all of the components are running in the same Windows NT domain.

Keywords: kbbug kbfix kbsna400presp4fix kbqfe kbsna400sp4fix KB240762

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