Catalog Services—the Global Catalog

By Author: Mike Jones
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Active Directory allows users and administrators to find objects such as files, printers, or users in their own free 70-620 test questions. However, finding objects outside of the domain and across the enterprise requires a mechanism that allows the domains to act as one entity. A catalog service contains selected information about every object in all domains in the directory, which is useful in performing searches across an enterprise. The global catalog is the catalog service provided by Active Directory.
The global catalog is the central repository of information about objects in a tree or forest. By default, a global catalog is created automatically on the initial domain controller in the first domain in the forest. A domain controller that holds a copy of the global catalog is called a global catalog sewer. You can designate any domain controller in the forest as a global catalog server. Active Directory uses multimaster replication to replicate the global catalog information between global catalog servers in other domains. It stores a full replica of all object attributes ...
... in the directory for its host domain and a partial replica of all object attributes contained in the directory for every domain in the forest. The partial replica stores attributes most frequently used in search operations (such as a user's first and last names, logon name, and so on). Attributes are marked or unmarked for replication in the global catalog when they are defined in the Active Directory how to get windows vista for free. Object attributes replicated to the global catalog inherit the same permissions as in source domains, ensuring that data in the global catalog is secure.
When a user logs on to the network, the global catalog provides universal group membership information for the account to the domain controller processing the user logon information. If there is only one domain controller in a domain, the domain controller holds the global catalog server. If there are multiple domain controllers in the network, one domain controller is configured to hold the global catalog. If a global catalog is not available when a user initiates a network logon process, the user is able to log on only to the local computer unless the site has been specifically configured to cache universal group membership lookups when processing user logon attempts.

The global catalog is designed to respond to user and programmatic queries about objects anywhere in the domain tree or forest with maximum speed and minimum network traffic. Because a single global catalog contains information about all objects in all domains in the forest, a query about an object that is not contained in the local domain can be resolved by a global catalog server in the domain in which the free exam papers is initiated. Thus, finding information in the directory does not produce unnecessary query traffic across domain boundaries.