APPC/CPI-C Application Does Not Use APPC LU With Auto-activated Sessions (306876)


The information in this article applies to:

  • Microsoft Host Integration Server 2000
This article was previously published under Q306876

SYMPTOMS

An Advanced Program-to-Program Communication (APPC) or Common Programming Interface for Communications (CPI-C) application may fail to allocate a conversation even though there are auto-activated (or pre-allocated) LU 6.2 sessions available for the remote APPC LU and APPC mode specified by the application.

The specific errors returned by the application may vary when this occurs. The following are typical APPC and CPI-C errors returned to the application.

If this occurs with an APPC application, the [MC_]ALLOCATE fails with the following error message:
primary_rc = 0x0003 (AP_ALLOCATION_ERROR)
secondary_rc = 0x00000005 (AP_ALLOCATION_FAILURE_RETRY)
A CPIC application fails with the following error message:
rc = 20 (CM_PRODUCT_SPECIFIC_ERROR)
In addition, the following event may also be logged in the Application Event log:
Event ID: 93
Source: SNA APPC Application
Description: APPC local conversation start failed:

Primary_rc = 0003
Secondary_rc = 00000005
TP_ID = <value>
Dest TP name = <value>
LU alias = <value>
PLU alias = <value>
Mode name = <value>
FQ PLU name = <value>
NOTE: These particular errors are fairly common APPC and CPI-C errors, so they may occur for reasons other then the one described here.

APPC or CPI-C applications that had been functioning correctly when the application was obtaining LU 6.2 sessions through a Microsoft SNA Server 3.0 or 4.0 system may start experiencing this problem when the SNA Server systems are upgraded to Host Integration Server 2000 because this particular problem does not exist in previous versions of SNA Server.

CAUSE

The SNA Server service (Snaservr.exe) in Host Integration Server 2000 does not properly initialize a variable under some circumstances. This prevents the SNA Server service from selecting the "best" local APPC LU for an LU 6.2 (APPC) session request.

RESOLUTION

To resolve this problem, obtain the latest service pack for Host Integration Server 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

328152 How to Obtain the Latest Host Integration Server 2000 Service Pack

The English version of this fix should have the following file attributes or later:

File nameDateTime
Snaservr.exe08/31/200103:51PM

NOTE: Because of file dependencies, the most recent fix that contains the preceding files may also contain additional files.

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Host Integration Server 2000 Service Pack 1.

MORE INFORMATION

The problem described here occurs under the following circumstances:
  • The APPC mode that is used by the APPC or CPI-C application is configured to auto-activate LU 6.2 sessions.
  • Explicit APPC partnerships are configured in the APPC mode that the application is using.
  • The local APPC LUs defined in SNA Manager have the Member of Default Outgoing Local APPC LU Pool option enabled.
  • The APPC or CPI-C application does not specify a default local APPC LU alias in its LU 6.2 session request.
The following is an example of such an SNA configuration:

Local APPC LUs:

LU aliasNetwork nameLU name
LOCAL1APPNLOCAL1
LOCAL2APPNLOCAL2

Both of the local APPC LUs are configured to be members of the default outgoing local APPC LU pool.

Remote APPC LUs:

LU aliasNetwork nameLU name
REMOTE1APPNREMOTE1
REMOTE2APPNREMOTE2


The session limits for APPC Mode APPCMODE are defined as follows:

Parallel session limit8
Min. contention winner limit4
Partner min. contention winner limit0
Automatic activation limit4


The following explicit APPC partnerships are defined for APPCMODE:

ServerLocal LUPartner LUConnection
SERVER1LOCAL1REMOTE1HOST
SERVER1LOCAL2REMOTE2HOST

When you are using this configuration, SNA Server 3.0 or 4.0 and Host Integration Server 2000 will auto-activate four sessions over each of the two explicit APPC partnerships that are defined for APPCMODE when the connection (HOST) is activated.

When SNA Server 3.0 or 4.0 receives a session request from an APPC or CPI-C application that specifies a remote APPC LU of REMOTE1 and mode APPCMODE, the SNA Server will return LOCAL1 as the local LU alias to use for the LU 6.2 conversation. This occurs because there are four contention winner sessions auto-activated for the APPC triplet LOCAL1/REMOTE1/APPCMODE that is currently available.

Under the same conditions, Host Integration Server 2000 may return LOCAL2 to the application as the local LU alias to use instead of LOCAL1. If LOCAL2 is not a valid APPC LU for the host application being used, the APPC [MC_]ALLOCATE will fail as described previously. Even if LOCAL2 is valid, it may not be desirable to use LOCAL2 with REMOTE1.

Any of the local APPC LUs that are members of the default outgoing local APPC LU pool are valid to use with any remote APPC LU and APPC mode because of the way that SNA Server 3.0/4.0 and Host Integration Server 2000 dynamically partner APPC LUs. However, a local APPC LU that has an available contention winner session with the requested remote APPC LU and mode should be the preferred local APPC LU. Auto-activated sessions are contention winner sessions.
Modification Type:MinorLast Reviewed:3/23/2005
Keywords:kbBug kbfix kbHostIntegServ2000preSP1fix kbHostIntegServ2000SP1fix KB306876 kbAudDeveloper
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