Importance

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Abstract

An event alerter system for notifying one application or process of a change in a database. A database management system includes an event generator that defines events to be reported, such as a change in a particular field of the database. Each time an change occurs, the event generator notifies an event manager of the name of the event. Whenever an event dependent process indicates an interest in a change in a field in a particular record or records in a database, it transfers a command to the event manager identifying each such record and change. When the event dependent process issues such a command, it enters a wait state to process the occurrence of an event in either a synchronous or asynchronous mode. The event manager converts such a command into entries in an event table that identifies, for that and other event dependent processes, the list of events in which a process has an interest. Thereafter, each time the event generator signals a change, the event manager examines the event table to determine which, if any, event dependent processes have an interest in that particular change and only three event dependent processes that have requests for being notified of the change pending. Then the event dependent process can obtain a message containing the status of each event in which it has an interest.

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First Claim