January 17, 2010

SMS: WMI terms and concepts

WBEM is a unifying architecture that allows access to data from a variety of underlying technologies - including Win32, WMI, the Desktop Management Interface (DMI), and the Simple Network Management Protocol (SNMP). WBEM is based upon the Common Information Model (CIM) schema, which is an industry standard driven by the Desktop Management Task Force (DMTF).

The Systems Management Server Site Database, Administrator Console and the Client Hardware Inventory component all depend on WMI.

WBEM provides a three-tiered approach for collecting and providing management data. This approach consists of a standard mechanism for storing data (a CIM-compliant database), a standard protocol for obtaining and disseminating management data (COM/DCOM; other protocols are also possible and under investigation), and a Win32 DLL known as a WBEM provider.

A component of the CIM (Common Information Model) is the CIMOM (Common Information Model Object Manager) repository. This datastore is where providers determine how to retrieve their information.

Although not technically accurate, it helps to think of the CIMOM in terms of a database. Definitions of WMI terms, and the corresponding concept in database terminology are in the following list.

WBEM term WBEM definition Database term
Namespace A collection of all classes. Database

Class Describes datatypes in a
schema. Object class definition. Table
Properties A single attribute of a class. Column
Instance One object of this class type. Row
Value The data for a property of a Field
specific instance.

Providers and WBEM
A WBEM provider supplies instrumentation data for parts of the CIM schema. Microsoft has written the WMI provider (a WBEM provider) that interfaces with the kernel mode WMI component. The kernel mode WMI component provides services that allow WMI-enabled drivers to implement WMI, and also acts as an interface to the WMI provider.

Systems Management Server uses the SMS Site Provider as the mechanism between the SMS Administrator's Console and the site server's SQL database. The Systems Management Server Hardware Inventory Client component uses the WMI Win32 provider.

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