HP Labs Technical Reports



Tuning the Reactivity of Database Monitors

Risch, Tore

HPL-90-17

Keyword(s):

Abstract: Database Monitors allow application programs to asynchronously monitor result changes of database access queries by associating tracking procedures with the queries. Whenever some application process U commits updates that the DBMS suspects will change significantly the result of a query monitored by a monitoring process M, the DBMS will invoke the associated tracking procedure of M. The invocation is asynchronous so that the updating process U is autonomous from the monitoring process M. This paper first gives a formalization of the concept of database monitors. Then we define the Reactivity as a measure of how often a given Tracking Procedure will be invoked. Some Tuning Parameters are introduced that give the programmer a means to adjust the reactivity. The settings of these parameters adapt the behavior and the performance of database monitors to the needs of particular applications. High reactivity will allow fine grain tracking but it will also decrease the performance of the application, the DBMS, and the communication network. By lowering the reactivity we gain efficiency at the expense of loosing information. The use of tuning parameters is exemplified for two implemented prototype applications.

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