What is DCOM and Why Do I Need It?

 

Last Revised: 2/20/02         By: REW

 

Keywords: DCOM, installation, database, DDE, OLE, dll, Windows®95, Windows®98, operating system

 

The information in this article applies to:

• Microsoft’s Distributed Component Object Model (DCOM) - DCOM95.EXE v4.71.1015.0

 

 

Summary

This article explains the importance of DCOM and its significance in relation to DataLyzer® Spectrum Software.

 

What is DCOM?

DCOM is a technology created by Microsoft that “enables software components [ActiveX components] to communicate directly with each other across networks” and first became available in Windows NT 4.0. In many respects, it is an extension of COM/ActiveX technology across a broader range of networks.

 

DCOM in the next evolutionary step that Microsoft has taken towards object technology. The previous technologies that DCOM builds upon are DDE (Dynamic Data Exchange, a form of messaging between Windows program), OLE (Object Linking and Embedding, putting visual links between programs within an application), COM (Component Object Model, used as the basis for all object binding), and ActiveX (COM enabled for the Internet).

 

Why is DCOM Necessary?

DCOM, among other things, updates OLE32.DLL, which consists of the core functions of Object Linking and Embedding. The updates made to OLE32.DLL are required by OLE DB 2.0 (which is one of the core technologies included in MDAC 2.5) and other technologies in MDAC.

 

DCOM95.EXE version 4.71.1015.0 is a file provided by Microsoft that will install the new DCOM technology on Windows95 systems. Windows98 shipped with an older version of DCOM, however, in order to run properly with MDAC 2.5, version 4.71.1015.0 is required.

 

Note that Windows NT 4.0 will need Service Patch 3 in order to have a version of DCOM that allows MDAC 2.5 to run smoothly. You should NOT install DCOM95.EXE on Windows NT.

 

The DataLyzer® Spectrum setup program tests for the need to install DCOM, the program looks in the Windows Registry for a key called:

 

“HKEY_CLASSES_ROOT\CLSID\{bdc67890-4fc0-11d0-a805-00aa006d2ea4}\InstalledVersion”

 

and checks to see if the key value is greater than or equal to “4,71,0,2612”. If it isn’t, then the setup program launches a silent install of DCOM95.EXE.

 

“DCOM The Distributed Component Object Model ©1997 Microsoft”, Conference White Papers, MSDN Library Visual Studio 6.0a

For information on MDAC please see the Application Note: “What is MDAC and why do I need it?”

 

The command used: DCOM95.EXE /R:N /Q:U

 

Installing DCOM95 Manually

To install Microsoft Distributed Component Object Model (DECOM) from the CD, follow these steps:

 

1. In Windows Explorer open the DataLyzer® Spectrum CD.

2. Locate and open the directory MSINSTALL in the root directory of the CD.

3. Click on the file DCOM95.EXE. This will run an installation routine for the Microsoft Distributed Component Object Model. Select full installation. Proceed selecting defaults.

 

When this routine is done attempt to run the DataLyzer® Spectrum module.

 

 

 

DataLyzer® Spectrum Application Note

Compliments of DataLyzer International, Inc.

 

Control Number: 76