FIX: Access Violation When You Migrate MTS Application to COM+

When you migrate a Microsoft Transaction Server (MTS) application to COM+, and you do not call the SetComplete or SetAbort method, an Access Violation may occur, and the application may fail (crash). This problem occurs in COM+ (Windows 2000 Service Pack 1) and not in MTS.

This problem occurs when non-root transactional objects release the object reference to their parent object and do not call SetComplete or SetAbort explicitly at the end of the method.

This problem is caused by a difference in the activation and deactivation mechanisms between COM+ and MTS. In COM+, if the child object does not set the done bit to true (if it does not call the IObjectControl::SetComplete or the IObjectControl::SetAbort method, does not call the IContextState:setCompletion method, or does not use Auto-Completion), the COM+ interception layer deactivates the parent object before the child object. In fact, you do not need to set the done bit, even if it is preferred in most situations.

To resolve this problem, obtain the latest service pack for Windows 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

Microsoft has confirmed that this is a problem in Microsoft Windows 2000. This problem was first corrected in Windows 2000 Service Pack 2.

Steps to Reproduce Behavior

1. Create a dynamic-link library (DLL) with three objects: Root, Parent, and Child. Set the transaction attribute to Requires a transaction.
2. The client calls CoCreateInstance on the first Root object.
3. The client calls the Root::RootMethod method.
4. In Root::RootMethod, use the CreateInstance method of the ObjectContext object to create the Parent object in the context of MTS. Then call the Parent::ParentMethod method.
5. In the Parent::Activate method, call CCI on Child, or ObjCtx.CreateInstance in MTS, and then call Child::SetOwner(this), or SafeRef(this) in MTS.
6. In the Child::Activate method, save the reference to Parent in the myOwner member variable.
7. In Parent::ParentMethod, call the Child::ChildMethod method.
8. In Child::ChildMethod, return without calling SetAbort or SetComplete.
9. In the Child::DeActivate method, release its reference to its owner object Parent.
10. In the Parent::DeActivate method, release its reference to Child.
11. Call Child::DeActivate.

NOTE: The Access Violation occurs in COM+ because step 10 occurs before step 9.