Database systems which support preorchestrated multimedia presentations must be able to adapt the resource demand or ececuting presentations. Such adaptations ca be dictated by underlying resource management components. When resources are not reserved, such adaptations are necessary to overcome fluctuating resource availability. Adaptations across components of presentations as well as across concurrent sessions have to be considered in the context of the individual needs of presentation providers and viewers. This paper describes the general concept of Reactive Playout Management (RPM) which provides an application-independent service for adaptive multimedia presentations. The PYLOT scheme (PlaYout Load OpTimization scheme) is proposed which enables RPM in best-effort architectures. In particular, the global allocation routine of PYLOT is elaborated. This routine allocates load shares which sessions must give up or may add on according to replugable adjustment strategies. In an optional post-optimization step, the routine manipulates the load proportions such that minimal total adjustment costs and maximal total adjustment profit are achieved, respectively. This optimization is demonstrated by experimental results.

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