Q246723: How to Programmatically Timeout an (MC_)ALLOCATE Verb
Article: Q246723
Product(s): Microsoft SNA Server
Version(s): WINDOWS:3.0,3.0 SP1,3.0 SP2,3.0 SP3,3.0 SP4,4.0,4.0 SP1,4.0 SP2,4.0 SP3
Operating System(s):
Keyword(s): kbsna300sp1 kbsna300sp2 kbsna300sp3 kbsna300sp4 sna4 kbsna400sp1 kbsna400sp2 kbsna400sp
Last Modified: 13-JUN-2001
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The information in this article applies to:
- Microsoft SNA Server, versions 3.0, 3.0 SP1, 3.0 SP2, 3.0 SP3, 3.0 SP4, 4.0, 4.0 SP1, 4.0 SP2, 4.0 SP3
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SUMMARY
=======
This article demonstrates how a developer can use the APPC WinAsyncAPPCEx()
function in combination with the Win32 WaitForSingleObjectEx() to expire an
(MC_)ALLOCATE verb when a predefined time-out interval has elapsed.
Microsoft does not recommend canceling an outstanding [MC_]ALLOCATE unless the
request has been outstanding for a reasonable period of time (at least 20
seconds). If [MC_]ALLOCATE is issued with rtn_ctl = AP_WHEN_SESSION_ALLOCATED,
the request does not complete until an available bound LU6.2 session is
allocated from an SNA Server computer that supports the Local LU/ Remote LU/Mode
being requested. A couple possible causes for slow [MC_]ALLOCATE response time
include the following:
- If all available LU6.2 sessions are already in use, then the [MC_]ALLOCATE
will block until a current conversation ends, creating an available LU6.2
session. If this is occurring frequently, consider increasing the parallel
session limit in the SNA Server Mode and the remote application subsystem.
- If the APPC LU session is supported through an on-demand connection, and the
connection is slow to activate (such as over SDLC)
Also, in order for the SNA Server computer(s) to properly handle cancelled
[MC_]ALLOCATE requests, the computer(s) should be running at least SNA Server
4.0 SP2 or greater. For additional information, click the article number below
to view the article in the Microsoft Knowledge Base:
Q195996 SNA Server Incorrectly Handles Cancelled Allocate Requests
MORE INFORMATION
================
When you use the following sample code, an APPC Allocate request will timeout if
it has not completed in 25 seconds. This code is used for demonstration purposes
only.
The following code snippet begins with construction of the verb control block
(vcb) used for the Allocate request. When the vcb is complete, a pointer to the
vcb is passed to the WinAsyncAPPCEx() function along with a Win32 handle used
for event notification. The handle that is passed to the WinAsyncAPPEx()
function is also registered with the WaitForSingleObjectEx(). The second
argument specified in the WaitFOrSingleObjectEx is the timeout value specified
in milliseconds. If the function succeeds, the return value indicates the event
that caused the function to return. If the return value is WAIT_TIMEOUT, then
the function completed as a result of the expired timer.
For more details concerning APPC Programming and Win32 APIs, please see the
Microsoft Platform SDK.
...
...
// Construct verb control block (vcb)
vcb->allocate.opcode = AP_B_ALLOCATE;
vcb->allocate.opext = AP_BASIC_CONVERSATION;
vcb->allocate.conv_type = AP_BASIC_CONVERSATION;
memcpy( vcb->allocate.tp_id,TPid, 8);
vcb->allocate.sync_level = AP_CONFIRM_SYNC_LEVEL;
vcb->allocate.rtn_ctl = AP_WHEN_SESSION_ALLOCATED;
FillMemory(vcb->allocate.plu_alias,sizeof(vcb->allocate.plu_alias),0x20);
CopyMemory(vcb->allocate.plu_alias,RLUName,strlen(RLUName) );<BR/>
FillMemory(vcb->allocate.mode_name,sizeof(vcb->allocate.mode_name),0x20);
CopyMemory(vcb->allocate.mode_name,ModeName, strlen(ModeName) );
ConvertAToE(vcb->allocate.mode_name, 8);
FillMemory(vcb->allocate.tp_name, sizeof(vcb->allocate.tp_name), 0x20);
CopyMemory(vcb->allocate.tp_name, "GREGORY", 7);
ConvertAToE(vcb->allocate.tp_name,64);
vcb->allocate.security = AP_NONE;
// Create an unnamed event object
hHandle = CreateEvent(NULL, FALSE, FALSE, NULL);
// - Use async entry point for the verb.
// - Pass the event handle (created above) along with pointer to vcb
verbid = WinAsyncAPPCEx(hHandle,(long)vcb);
if (verbid == 0)
{
return false;
}
// Sleep for 25 seconds before timing out
wait_code = WaitForSingleObjectEx(hHandle,25000,true);
ASSERT(wait_code != WAIT_ABANDONED);
if (wait_code == WAIT_TIMEOUT)
{
//failed
WinAPPCCancelAsyncRequest(verbid);
CloseHandle(hHandle);
return false;
}
CloseHandle(hHandle);
// Allocate successful. Return and do more useful things
return true;
}
...
...
Additional query words:
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Keywords : kbsna300sp1 kbsna300sp2 kbsna300sp3 kbsna300sp4 sna4 kbsna400sp1 kbsna400sp2 kbsna400sp3
Technology : kbAudDeveloper kbSNAServSearch kbSNAServ300 kbSNAServ400 kbSNAServ300SP3 kbSNAServ300SP1 kbSNAServ400SP1 kbSNAServ400SP2 kbSNAServ400SP3 kbSNAServ300SP2 kbSNAServ300SP4
Version : WINDOWS:3.0,3.0 SP1,3.0 SP2,3.0 SP3,3.0 SP4,4.0,4.0 SP1,4.0 SP2,4.0 SP3
Issue type : kbinfo
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