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The Change Log feature in Windows SharePoint Services 3.0 can be used by multiple third-party applications to synchronize with SharePoint sites. In Windows SharePoint Services 2.0, a search often required a full crawl of the site, which resulted in greater latency of search results and higher bandwidth and CPU costs. In Windows SharePoint Services 3.0, search is based on precise indexing of changed objects. This provides results more quickly and with lower overhead.
Change Log Functionality
The change log returns a list of SPChange* objects for changes that happened, for example, to the following object types:
Items, files, and folders
The change log does not record changes to the following settings or objects:
Web application configuration
Global administration settings
Web Parts and safe controls
Web site, site collection, content database, or Web application configuration
The change log contains information about the following types of item change:
The change log can be accessed at the following, progressively inclusive, scopes:
Change Log Security
The Change Log is not security-trimmed based on the caller's privileges: Information disclosure is avoided by returning only IDs in the log. Note, however, that when executing front-end object model code on behalf of a user whose permission to view an item was revoked, the Change Log provides a way to track items by ID. Consumers of the log should issue queries against lists by using the SPQuery class to ensure that security-trimmed enumerations are returned.
Change Log Freshness
Callers should not expect the Change Log to return items with precision. In some cases, the log returns items only up to a particular point in the past. Callers receive a token for the time up to which the Change Log returns items.
To correctly log move operations, the Change Log registers the following changes:
Folder move: MovedAway event on the source list, MovedInto event on the destination list
Site move: MovedAway event on the source site, MovedInto event on the destination site
The Change Log is a physical table in each content database, and each transaction writes to the log. The Change Log can be accessed through the GetListItemChangesSinceToken method of the Lists Web service to get changes starting from a specified point in time.