APPC/5250 Hot Backup Fails If the Connection Is Inactive or Pending (185540)

SYMPTOMS

APPC/5250 applications connecting to SNA Server computers that are configured for APPC Load Balancing and Hot Backup may fail to connect to a remote system if one or more of the configured connections to the remote system are in an Inactive or Pending state. This occurs even though other connections to the remote system are in an Active state.

The error returned by the APPC/5250 application when this problem occurs may vary. The 5250 utility included with SNA Server generates the following error message when this problem occurs:

   Could not connect to the remote host.
   [0003][00000004]

In addition, the following message may be written in the Windows NT Server application event log if the APPC/5250 application is run on SNA Server or on an SNA Server Windows NT Client:

   Event ID: 93
   Source: SNA APPC Application
   Description: APPC local conversation start failed:

Primary_rc = 0003 Secondary_rc = 00000004 TP_ID = 00000000C0452500 Dest TP name = 30F0F0F5 LU alias = <Local APPC LU Alias> PLU alias = <Partner APPC LU Alias> Mode name = <APPC Mode Name>

For additional information about configuring SNA Server for Load Balancing and Hot Backup for both 3270 and APPC sessions, please see the following article in the Microsoft Knowledge Base:

128244 SNA Server Load Balancing and Hot Backup

CAUSE

The APPC library is responsible for locating an available LU 6.2 session that matches the parameters (Local APPC LU and Remote APPC LU, for example) requested by the application. If there are multiple SNA Server computers that can provide the requested Local and/or Remote APPC LUs, the APPC Library contacts the SNA Server computers in a random order according to how the servers are listed in the SNA Client's Service Table. The SNA Server computer can respond to the session requests with various errors depending on the state of its configured connections and the availability of the LU 6.2 sessions on those connections.

When the APPC library receives these error responses from the available SNA Server computers, it ranks the errors it receives to determine which SNA Server computer has the greatest probability of providing the requested LU 6.2 session.

This problem occurs when SNA Server receives an LU 6.2 session request for sessions that are defined to use a connection that is in an Inactive or Pending state. The SNA Server service returns an error to the APPC Library that is the same error that it returns for an Active connection that does not currently have any suitable active LU 6.2 sessions available. Therefore, the APPC library ranks these Inactive and/or Pending connections at the same level as Active connections. If one of these Inactive or Pending connections is identified as the best connection, the APPC/5250 application will fail to get a session.

RESOLUTION

SNA Server 3.0

To resolve this problem, obtain the latest service pack for SNA Server version 3.0. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

184307 How to Obtain the Latest SNA Server Version 3.0 Service Pack

SNA Server 4.0

This problem has been corrected in the latest U.S. Service Pack for SNA Server version 4.0. For information on obtaining the Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

   S E R V P A C K