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COM+ stores all the information about an application in a persistent storage called the COM+ catalog (henceforth, simply the catalog).
The catalog uses two different stores:
the Windows registry (HKEY_CLASSES_ROOT)
the COM+ registration database (called RegDB)
When a component is installed in the catalog, the classic COM aspects of registration, such as the PROGID of the class and the complete path to the component DLL, are stored under the Windows registry. The Windows reg-istry is also used to store the type library and proxy/stub information. All other configuration attributes are stored in the RegDB database. This split-registration makes it easy to migrate existing components (components based on classic COM) into the catalog without having to rebuild the component.
The catalog stores the configuration attribute at the application level, the component level, the interface level, as well as the interface method level. These configuration settings help an application specify and use various COM+ services such as transactions, synchronization, security, object pooling, JIT activation, component queuing, and COM+ events.
To access the catalog, COM+ provides an administrative component called the Catalog Manager. The Catalog Manager exposes a set of automation objects collectively referred to as the COMAdmin objects. Using these COMAdmin objects, you can read and write information that is stored in the catalog and perform tasks such as:
install and configure COM+ applications
manage installed COM+ applications
manage and configure COM+ services
export existing COM+ applications for deployment to other machines
remotely administer component services on a different machine
The COMAdmin objects can be used to develop either lightweight scripts or general-purpose administration tools. For example, you can:
write scripts to perform routine administrative tasks
develop tools to administer and monitor component services
create installation programs for your COM+ applications
In fact, the Component Services snap-in itself is just a convenient graphical front-end that is based on the COMAdmin objects.
On each Windows 2000 machine there is a COM+ catalog server running as a component in the system application. The catalog server controls access to the catalog data stored on the local machine. The catalog server essentially is a query engine that allows data to be read from and written to the catalog on that machine.
In order to access the catalog on a machine, a session has to be opened with the catalog server on that machine. As we will see shortly, one of the COMAdmin objects lets us do just this.
Let s look at the COMAdmin objects in detail.
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