SNA Server Support for ACTPU (ERP) and ACTLU (ERP)
ID: Q138469
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The information in this article applies to:
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Microsoft SNA Server, versions 2.0, 2.1, 2.11, 3.0, 4.0
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:
- Start Registry Editor (Regedt32.exe or Regedit.exe, as appropriate for
your version of Windows NT).
- Go to the following key in the registry:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\SnaServr\Parameters
- On the Edit menu, click Add Value and use the following entry:
Value Name: ACTPUERP
Data Type: REG_SZ
- Click OK.
- 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.)
- Exit the Registry Editor.
- 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
Keywords : kbnetwork sna3270 sna211 sna3 sna4 sna2 sna21
Version : WINDOWS:2.0,2.1,2.11,3.0,4.0
Platform : WINDOWS
Issue type :
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