99 Copyright © 2011, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. Chapter 6 DOI: 10.4018/978-1-60960-553-7.ch006 INTRODUCTION Replication techniques are used to provide multiple critical copies and to maintain them. In coherent state, they improve the overall system availability and performance. In splitting of replication advantages, there are many problems that must be resolve like (Gray et al. 1996; Xu et al. 2002): • How do we select and estimate the metrics for taking replication decisions? Ghalem Belalem University of Oran (Es Senia), Algeria Dynamic Negotiation Mechanism for Improving Service Quality for Replicas in Data Grids ABSTRACT In order not to be limited in term of calculation, storage and communication, the concept of grid, which does not cease evolving, makes it possible to offer a practical operation of work unifed as well as a great storage and computing power. To manage the division in the data grid, technical replication is used, but in spite of their advantages, the competitor access to the data could involve inconsistencies, from where the great challenge to ensure the consistency management between replicas of object. In this chapter, we describe model double-layered adapted to the applications on a large scale and which represents the support of the hybrid approach of consistency management of replicas based on pes- simistic and optimistic approaches. This hybrid approach present an adapted mechanism based on the various negotiation forms between virtual consistency agents to be able to reduce the number of conficts between replicas in data grids.