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Q138469: SNA Server Support for ACTPU (ERP) and ACTLU (ERP)

Article: Q138469
Product(s): Microsoft SNA Server
Version(s): WINDOWS:2.0,2.1,2.11,3.0,4.0
Operating System(s): 
Keyword(s): kbnetwork sna4
Last Modified: 12-JUN-2001

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The information in this article applies to:

- Microsoft SNA Server, versions 2.0, 2.1, 2.11, 3.0, 4.0 
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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 NT 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 (used for
  applications and data transfer after the user has logged on to an
  application) if the PLU-SLU session is active.

- 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 is issued by the host, SNA Server resets all
  the sessions using that PU, which is all the 3270 sessions.

- If an ACTPU (ERP) command is issued by the host, SNA Server only resets 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 defined.

NOTE: Starting with SNA Server 2.11 Service Pack 2, the default behavior for SNA
Server was changed so that ACTPU (ERP) support is not enabled by default. For
more information on why the default behavior was changed, see the following
Microsoft Knowledge Base article:

  Q153253 SNA Server 3270 Sessions Not Recovered with Eicon WAN Server

Add the following Registry Entry to enable ACTPU (ERP) support in SNA Server:

1. Start Registry Editor (Regedt32.exe or Regedit.exe, as appropriate for your
  version of Windows NT).

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" (without the quotation marks)

4. Click OK.

5. In the String field, input the string TRUE and then click OK. (Actually, any
  value can be entered for the String to enable ACTPU (ERP) support.)

6. Exit the Registry Editor.

7. Stop and restart the SNA Server service.

If the ACTPUERP registry entry is not set, SNA Server treats all ACTPU requests
as ACTPU (Cold) requests.

SNA Server 4.0 and later
------------------------

A change was incoporated in SNA Server 4.0 that changed the default behavior in
SNA Server so that ACTPU(ERP) support is enabled by default like it was prior to
SNA Server 2.11 SP2. With SNA Server 4.0 and later, ACTPU(ERP) support is
disabled by adding the ACTPUERP registry and setting its Value to NO, 0, OFF, or
FALSE. These values are not case sensitive so they may be entered in lower case
as well.


NOTE: For information describing the ACTPU and ACTLU message formats, see the IBM
SNA Formats Guide (IBM p/n# GA27-3136), Chapter 5, "Request/Response Units
(RUs)".

Additional query words: prodsna

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Keywords          : kbnetwork sna4 
Technology        : kbAudDeveloper kbSNAServSearch kbSNAServ300 kbSNAServ200 kbSNAServ211 kbSNAServ400 kbSNAServ210
Version           : WINDOWS:2.0,2.1,2.11,3.0,4.0

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