The present invention relates to a system and a method performed in a client-server computing environment for managing the access requested by user applications (10) to a central, non-standard database type data repository (22) having proprietary access and data structures, in which data repository (22) the data integrity is controlled and checked by a further “mature” application running independently of the user applications (10). In order to provide an improved, cost-effective multiple-user access method, the following steps are proposed: a) performing a first update on said data repository (22) of a first user application (10A) in a transactional form, and b) in case a second user application (10B) requests a second update of said repository (22) during said first update transaction, c) blocking a write access until said first update's transaction has been completed.