  DCOM RPC Failure? 
 The Question is:
 
OpenVMS DCOM question
 
Our company has been using OpenVMS for its flagship SCADA product for nearly 20
 years.  However, we are increasingly offloading advanced functionality to
 Windows machines since 3rd party vendor support is far better.
 
In searching for a middleware solution between OpenVMS and Windows we decided
 to use DCOM for OpenVMS as of June 2001.  Our initial results looked quite
 good with the latest OpenVMS and DCOM version (1.1) available at that time.
 
But as of late, we have experienced numerous problems with DCOM at OpenVMS (see
 REF note 1.3.1 below).  Our staff determined the VMS RPC daemon would fail
 after a small number of DCOM transactions.  So we installed the various
 patches from your website an
d we believe the RPC daemon problem has been solved.
 
However, we are also seeing a problem with CoCreateInstanceEx(), where an
 "access denied" error occurs after a number of successful DCOM transactions.
 Our DCOM client was designed to do a CoInitializeEx() into an MTA apartment,
 followed by a guaranteed C
oUninitialize() after the transaction completed.  By experimentation, we
 discovered that moving the calling thread into an MTA apartment and leaving it
 there appears to solve the "access denied" problem.  Although we can accept
 this workaround, this behav
ior does not conform to the COM specification.
 
Any comments are appreciated.
 
Sincerely,
 
John Petz
Transdyn Controls, Inc
Atlanta, GA
678/473-6456
 
RE: 1.3.1 Windows 2000 Interoperation Requires Compaq DCE Version 3.0 for OpenVMS
As part of our interoperability testing, HP has identified a problem in the
 authentication layer that prevents authenticated COM requests between an
 OpenVMS COM client application and a Windows 2000 COM server application. In
 this case, the system returns
 an 80070005 (E_ACCESSDENIED) error from a call to CoCreateInstanceEx in the
 COM client application. The problem does not occur with requests between
 Windows 2000 COM client applications and OpenVMS COM server applications.
 
The solution to this problem is to install the Compaq DCE Version 3.0 for
 OpenVMS kit. (COM needs only the RPC run time, but to get the RPC run time you
 must install the DCE kit.)
 
This problem occurs only on versions of OpenVMS prior to Version 7.3. The DCE
 for OpenVMS Version 3.0 RPC run time ships with the OpenVMS operating system
 beginning with OpenVMS Version 7.3. If you are running OpenVMS Version 7.3 or
 higher, you do not nee
d to install the DCE kit.
 The Answer is :
 
  Assuming you have the current ECO kits for OpenVMS, TCP/IP Services
  and DCE, please contact the support center directly for assistance
  with this resolution.
 
 Answer written or last revised on  8-MAR-2004 
