COM+
COM+ is a technology stack, built approximately like this:
| Buzzword | Service |
|---|---|
| COM+ | load balancingobject poolingIMDBMSMQeventsadministration |
| MTS | transactionsresource poolingrole-based securityJust-In-Time Activationadministration |
| DCOM | remote architecturedistributed component service |
| COM | interface-based programming |
DCOM failed in the marketplace, taking out most of the stack above it.
Microsoft built a monument on top of COM, a lot of which is deprecated now. This was motivated by Windows DNA, parts of which are still around.
COM+ and DNA are terms that overlap. The way I think of it is, COM+ is this specific technology stack, and DNA is more of a marketing term that means “whatever tools make up a 3-tier application”. This includes IIS and SQL Server. The list of COM+ objects is a little more tangible.