A method to optimize primary and secondary read cache in a data replication environment includes determining contents of a primary read cache at a primary site. The method updates a primary cache map describing the contents and transmits the primary cache map from the primary site to a secondary site. At the secondary site, the method uses the primary cache map to substantially synchronize a secondary read cache with the primary read cache. The method further monitors for updates to the primary read cache and updates the primary cache map accordingly. When a difference between a current primary cache map and a previously transmitted primary cache map reaches a threshold, the method transmits the current primary cache map from the primary site to the secondary site. A corresponding system and computer program product are also disclosed.