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Configuring COM+ Application Pooling Values

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You can use the following instructions to configure COM+ application pooling values for your COM+ application.

Note

Library applications have the recycling and pooling properties of their host process.

 

Component Services Administrative Tool

To configure COM+ application pooling for a COM+ application, use the following steps:

  1. In the console tree of the Component Services administrative tool, right-click the COM+ application you want to be pooled and then click Properties.

  2. On the Pooling & Recycling tab, under Application Pooling, enter a value for Pool Size, depending on the number of instances of your application that you want to have running.

  3. Click OK.

Visual Basic

The following function in Visual Basic demonstrates how you can set the COM+ application pooling value (represented by its ConcurrentApps property) for any COM+ server application that you choose. To use it from Visual Basic, add a reference to the COM+ Admin Type Library.

Function SetMyApplicationPooling( _
  strApplicationName As String, _
  lngPoolValue As Long _
) As Boolean  ' Return False if any errors occur.

    SetMyApplicationPooling = False  ' Initialize the function.
    On Error GoTo My_Error_Handler  ' Initialize error handling.

    Dim objCatalog As COMAdmin.COMAdminCatalog
    Dim objAppCollection As COMAdmin.COMAdminCatalogCollection
    Dim objApplication As COMAdmin.COMAdminCatalogObject
    Set objCatalog = CreateObject("COMAdmin.COMAdminCatalog")
    Set objAppCollection = objCatalog.GetCollection("Applications")
    objAppCollection.Populate 
    For Each objApplication in objAppCollection
        If objApplication.Name = strApplicationName Then
            objApplication.Value("ConcurrentApps") = lngPoolValue
            MsgBox strApplicationName & _
              " pooling value set to " & lngPoolValue
            Exit For
        End If
    Next
    objAppCollection.SaveChanges

    Set objApplication = Nothing
    Set objAppCollection = Nothing
    Set objCatalog = Nothing
    SetMyApplicationPooling = True  ' Successful end to procedure
    Exit Function

My_Error_Handler:  ' Replace with specific error handling.
    MsgBox "Error # " & Err.Number & " (Hex: " & Hex(Err.Number) _
      & ")" & vbNewLine & Err.Description
    Set objApplication = Nothing
    Set objAppCollection = Nothing
    Set objCatalog = Nothing
End Function

To use the function, provide a string value for the COM+ server application name and an integer value for the desired application pooling setting. The following Visual Basic code shows how to set the application pooling value to 15 for the application named "MyApplication":

Sub Main()
    If Not SetMyApplicationPooling("MyApplication", 15) Then
        MsgBox "SetMyApplicationPooling failed."
    End If
End Sub

C/C++

The following function in C++ demonstrates how you can set the COM+ application pooling value (represented by its ConcurrentApps property) for any COM+ server application that you choose. The ErrorDescription method is described at Interpreting Error Codes.

#include <windows.h>
#include <stdio.h>
#import "C:\WINDOWS\system32\Com\ComAdmin.dll"
#include "ComAdmin.h"
#include "StrSafe.h"  // For the StringCchLengthW function

BOOL SetMyApplicationPooling (OLECHAR* szMyApp, LONG lPool) {
    IUnknown * pUnknown = NULL;
    ICOMAdminCatalog * pCatalog = NULL;
    ICatalogCollection * pAppColl = NULL;
    ICatalogObject * pApplication = NULL;
    HRESULT hr = S_OK;
    BSTR bstrMyApp = NULL;
    unsigned int uMaxLen = 255;  // Maximum length of szMyApp
    LCID lLan = 1024;// Use the default language for comparing strings.

try {
    // Test the input pool value.
    if ((lPool < 1) || (lPool > 1048576)) throw(E_INVALIDARG);
    
    // Test the input szMyApp to make sure it's OK to use.
    hr = StringCchLengthW(szMyApp, uMaxLen, NULL);
    if (FAILED (hr)) throw(hr);
    
    // Convert szMyApp to a BSTR.
    bstrMyApp = SysAllocString(szMyApp);

    // Create a COMAdminCatalog object and get its IUnknown.
    hr = CoCreateInstance(CLSID_COMAdminCatalog, NULL, 
      CLSCTX_INPROC_SERVER, IID_IUnknown, (void**)&pUnknown);
    if (FAILED (hr)) throw(hr);

    // Get the ICOMAdminCatalog interface.
   hr = pUnknown->QueryInterface(IID_ICOMAdminCatalog, 
      (void**)&pCatalog); 
    if (FAILED (hr)) throw(hr);

    // Get an interface to the Applications collection.
    hr = pCatalog->GetCollection(L"Applications", (IDispatch**)&pAppColl);
    if (FAILED (hr)) throw(hr);

    // Populate all of the Applications collection.
    hr = pAppColl->Populate();
    if (FAILED (hr)) throw(hr);

    // Get the number of applications in the collection.
    LONG lCount = -1;
    hr = pAppColl->get_Count(&lCount);
    if (FAILED (hr)) throw(hr);

    // Iterate through each application in the collection.
    VARIANT varName;
    VariantInit(&varName);
    for (LONG lIdx = 0; lIdx < lCount; lIdx++) {
        hr = pAppColl->get_Item(lIdx, (IDispatch**)&pApplication);
        if (FAILED (hr)) throw(hr);

        // Get the Name value of each application.
       hr = pApplication->get_Name(&varName);
        if (FAILED (hr)) throw(hr);

        // Compare the application name to bstrMyApp.
        hr = VarBstrCmp(varName.bstrVal, bstrMyApp, lLan, NULL);
        if (FAILED (hr)) throw(hr);
        if (VARCMP_EQ == hr) {  // The strings are equal.
            // Set the new pooling value.
            VARIANT varPool;
            VariantInit(&varPool);
            varPool.vt = VT_I4;  // Tell the VARIANT it's holding a LONG.
            varPool.lVal = lPool;
            hr = pApplication->put_Value(L"ConcurrentApps", varPool);
            if (FAILED (hr)) throw(hr);
            printf("%S pooling value set to %ld.\n", bstrMyApp, lPool);
            break;
        }
    }
    LONG lNum;
    hr = pAppColl->SaveChanges(&lNum);
    if (FAILED (hr)) throw(hr);

    // Clean up.
    SysFreeString(bstrMyApp);
    pUnknown->Release();
    pUnknown = NULL;
    pApplication->Release();
    pApplication = NULL;
    pAppColl->Release();
    pAppColl = NULL;
    pCatalog->Release();
    pCatalog = NULL;
    return (TRUE);
}  // Try

catch(HRESULT hr) {  // Replace with specific error handling.
    printf("Error # %#x: ", hr);
    ErrorDescription(hr);
    SysFreeString(bstrMyApp);
    if (NULL != pUnknown) pUnknown>Release();
    pUnknown = NULL;
    if (NULL != pApplication) pApplication->Release();
    pApplication = NULL;
    if (NULL != pAppColl) pAppColl->Release();
    pAppColl = NULL;
    if (NULL != pCatalog) pCatalog->Release();
    pCatalog = NULL;
    return (FALSE);
}catch(...) {
    printf("An unexpected exception occurred.\n");
    throw;
}
}  // SetMyApplicationPooling

To use the function, provide a string value for the COM+ server application name and an integer value for the desired application pooling setting. The following C++ code shows how to set the application pooling value to 15 for the application named "MyApplication":

#define _WIN32_DCOM  // To use CoInitializeEx()
void main() {
    HRESULT hr = CoInitializeEx(NULL, COINIT_APARTMENTTHREADED);
    if (FAILED (hr)) {
        printf("CoInitializeEx failed: Error # %#x\n", hr);
        exit(0);  // Replace with specific error handling.
    }
    if (! SetMyApplicationPooling (L"MyApplication", 15))
        printf("SetMyApplicationPooling failed.\n");
    CoUninitialize();
}

COM+ Application Pooling Concepts