We consider the use of a cluster system for Application Service Provider (ASP). In the ASP context, hosted applications and databases can be update- intensive and must remain autonomous. In this paper, we propose a new solution for parallel processing with autonomous databases, using a replicated database organization. The main idea is to allow the system administrator to control the tradeoff between database consistency and application performance. Application requirements are captured through execution rules stored in a shared directory. They are used (at run time) to allocate cluster nodes to user requests in a way that optimizes load balancing while satisfying application consistency requirements. We also propose a new preventive replication method and a transaction load balancing architecture which can trade-off consistency for performance using execution rules. Finally, we discuss the on-going implementation at LIP6 using a Linux cluster running Oracle 8i.