MDAC 2.5 SDK - OLE DB Programmer's Reference
Chapter 19: OLE DB Services

Automatic Transaction Enlistment

It is not always apparent to the consumer when a provider is not automatically enlisted in transactions. Specifically, in the following cases enlistment does not occur:

• The provider does not support aggregation. To use OLE DB services, providers must support aggregation of all objects.
  
  
• The OLEDB_SERVICES registry entry does not exist. For information about how to add an OLEDB_SERVICES registry entry, see "Setting Provider Service Defaults."
  
  
• The provider has not enabled automatic transaction enlistment by assigning an appropriate value to the OLEDB_SERVICES registry entry. For more information, see "Overriding Provider Service Defaults."
  
  
• The provider does not support the ITransactionJoin interface.