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Windows Management Instrumentation (WMI) is the infrastructure for management data and operations on Windows-based operating systems. |
WMI is the Microsoft implementation of Web-based Enterprise Management (WBEM), which is an industry initiative to develop a standard technology for accessing management information in an enterprise environment. WMI uses the Common Information Model (CIM) industry standard to represent systems, applications, networks, devices, and other managed components as a set of objects and relations between them.
Refer to Microsoft's MSDN site for WMI architecture, availability on different operating systems, and other details.
Remote Management
WMI can be used to monitor and manage Windows computers remotely. Remote WMI connections are made through Distirbuted COM (DCOM). Remote computer should be properly configured to allow DCOM connections and execution of WMI requests. Refer to Configuring Remote Access to WMI and Configuring DCOM for Remote Access sections for details.
Uniform Model for Management Information
WMI is based on the Common Information Model that abstracts and describes the "managed environment" in terms of object-oriented paradigm. This model covers virtually all managed elements of modern IT environments including devices and their components, computer systems, operating systems, networks, software, users, physical environment, performance statistics. Thus, all manageable resources can be accessed in a common way. At the same time, CIM is extensible allowing vendors to represent their specific features.
WMI describes all manageable resources as objects that present element's data (readable properties) and controlling means (writable properties and methods). Every WMI object is an instance of some class. Classes define set of properties and methods their instances provide.
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For example, instances of Win32_Printer class present printer devices. This class defines few dozens of printer properties including its name, description, driver, capabilities, priority, status, various attributes, etc. Some of these properties are read-only, while others (like Priority, Direct, Hidden, KeepPrintedJobs, etc.) are writeable and can be used to configure printers via WMI. The Win32_Printer class also introduces several methods that allow to control printers: Pause, Resume, PrintTestPage, CancelAllJobs, etc. |
Events
Events are used by manageable resource and WMI infrastructure to notify monitoring/management systems about different kinds of changes. Event consumers should subscribe for events of interest specifying a filter. The filter describes conditions under which the consumer wants to receive notifications.
WMI Query Language
The WMI Query Language (WQL) is the Microsoft implementation of CIM Query Language (CQL), a query language for the Common Object Model. It is a subset of ANSI SQL with several changes to support WBEM/WMI. WQL allows to retrieve management information and subscribe for event notifications. Refer to WQL chapters in MSDN Library for details.
WMI Device Driver
WMI support in AggreGate Network Manager is provided by WMI device driver. The driver allows to:
| • | connect to WMI running on remote computers |
| • | retrieve WMI objects by WQL requests execution |
| • | fetch WMI classes and their instances |
| • | execute methods provided by WMI objects and vary their writable properties |
| • | subscribe to WMI event notifications using WQL requests and receive events from a WMI computer |
| • | run automatic actions in response to WMI events |
| • | cache WMI information on the server |
| • | store management information in database |
| • | discover WMI-enabled computers and configure them for monitoring and management. |