Database system with methodology for notifying clients of any additions, deletions, or modifications occurring at the database server which affect validity of a range of data records cached in local memory buffers of clients

摘要

Client/server system and methods are described for providing a "cache range" to database clients. When one or more records in a cache range of a client change, a server in connection with the client sends a notification that the cache range has changed. Instead of the client taking a lock out for updating a record, the client simply indicates to the server which records it is interested in (e.g., via registering an event alerter request), whereupon the server manages its resources as necessary to notify the client of a change in one of the records which is of interest to the client. The server can simply take out "interest" locks on the corresponding records; these are not locks which exclude the resource from other clients. Other clients are not prevented from accessing this resource (i.e., the records which are of interest). The interest lock is employed in conjunction with the registered event alerter for notifying the client when a range of records of interest is updated by another client. In this manner, the server undertakes action to indicate to the client when the client local buffer might be stale, thereby providing improved local record buffer management in a client/server database context.