Data Grids are becoming a popular infrastructure for distributed, data intensive scientific application. Data access optimization is one of the key features of such systems, as the transfer and access to the huge amounts of data are often the bottleneck of the data intensive tasks. Concept of replication, creation of multiple copies of a data source across multiple grid nodes, was adopted by grid community to increase data availability. In this paper, we present the ongoing work on the grid replica optimization framework that addresses both short-term and long-term replica optimization problems. We describe high level architecture of the optimization framework and discuss the promising results achieved by prototype implementation of several system components.