Although server technology provides a mean to support a wide range of online services and applications, their ad-hoc conguration poses signicant challenges to the perfor- mance, availability and economical costs of applications. One of the main concerns is that under a heavy load, the delay introduced by a server in the transaction process may grow unbounded. This paper precisely addresses this issue. First, we present the design of a server model as a non-linear continuous-time model. Second, we develop an admission control algorithm that allow to ensure a maximum average delay on the server. Model and control algorithm were implemented and applied on the standard PostgreSQL database server running the TPC-C warehouse application. The experiments show that the proposed method provides signicant benets for database servers management.