SNA Server Support for ACTPU (ERP) and ACTLU (ERP) (138469)


The information in this article applies to:

  • Microsoft SNA Server 4.0
  • Microsoft SNA Server 4.0 SP4
  • Microsoft Host Integration Server 2000
  • Microsoft Host Integration Server 2000 SP1
This article was previously published under Q138469

SUMMARY

If you have more than one mainframe attached to your Front End Processor (FEP) with Network Control Program (NCP) running, the IBM SNA "error recovery protocol" (ERP) can be used. This can be used for ownership takeover without interrupting the active LU-LU session.

For example, if the owning Service Control Point (SSCP) of PU/LU is down, the LU without active session becomes inactive. The other SSCP/mainframe can take the ownership of PU/LU without resetting the active LU-LU session by ACTPU(ERP) and ACTLU (ERP). And the other LU can now be activated by the new SSCP.

SNA Server supports the recovery of PLU-SLU sessions after receiving an ACTPU (ERP) and ACTLU (ERP) command. However, ACTPU (ERP) recovery requires that the SNA Server connection is not dropped. SNA Server reports connection failures by logging Event 23 in the Windows application event log. If the SNA Server connection to the FEP is lost, PLU-SLU session recovery is not possible.

MORE INFORMATION

SNA Server handles session recovery as follows, when receiving ACTPU and ACTLU commands:
  • When receiving an ACTLU (cold) command, SNA Server resets the SSCP-LU session (which is used to carry the logon screen) and the PLU-SLU session if the PLU-SLU session is active. (The PLU-SLU session is used for applications and data transfer after the user has logged on to an application.)
  • When receiving an ACTLU (ERP) command, SNA Server resets the SSCP-LU session. If there is an active PLU-SLU session, this session is left active.
  • The ACTLU (ERP) command is used in conjunction with the ACTPU (ERP) command. As for ACTLUs, if a cold ACTPU command is issued by the host, SNA Server resets all the sessions using that PU; SNA Server resets all the 3270 sessions.
  • If an ACTPU (ERP) command is issued by the host, SNA Server resets only the PU-SSCP session.
The SNA Server will send back an ACTPU (ERP) +RSP if all of the following are true:
  • An ACTPU (ERP) request was received.
  • The ACTPU (ERP) was received when the PU-SSCP session was already active.
  • The ACTPUERP Registry entry is not defined.
Add the following Registry Entry to disable ACTPU (ERP) support in Microsoft SNA Server 4.0 and Microsoft Host Integration Server 2000:
  1. Start Registry Editor (Regedt32.exe or Regedit.exe, as appropriate for your version of Windows).
  2. Go to the following key in the registry:

    HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\SnaServr\Parameters

  3. On the Edit menu, click Add Value and use the following entry:

    Value Name: ACTPUERP
    Data Type: REG_SZ

  4. Click OK.
  5. In the String field, enter the value NO, 0, OFF, or FALSE.

    These values are not case sensitive; you may use lower case.
  6. Quit Registry Editor.
  7. Stop and restart the SNA Server service.
If the ACTPUERP registry entry is set, SNA Server treats all ACTPU requests as ACTPU (Cold) requests.

REFERENCES

For information about the ACTPU and ACTLU message formats, see the IBM SNA Formats Guide (IBM p/n# GA27-3136), Chapter 5, "Request/Response Units (RUs)".
Modification Type:MajorLast Reviewed:3/31/2004
Keywords:kbnetwork KB138469
©2004 Microsoft Corporation. All rights reserved.