Distributed Database Management Systems offer advantages and new possibilities to centralized database systems. However, some aspects and issues need to receive further consideration. Concurrency control is one of these aspects that has to be improved in order to increase system performance. Strict Two Phase locking s2pl is the concurrency control mechanism that is used in most commercial database systems. The performance of s2pl can be greatly improved using speculative techniques with speculative Two Phase Locking algorithms sp2pl. In this paper we present extensions of the sp2pl algorithm based on Wait Depth Limited techniques wdl-sp2pl. A comprehensive simulation model is developed from which the performance of sp2pl and the wdl-sp2pl's are evaluated. Our analysis also shows that the new algorithms give a better performance than sp2pl, maintaining the robustness of sp2pl.