Systems. Methods, and Computer Program Products are provided managing a global cache coherency and reducing messaging traffic for coordination of access permissions in a distributed shared caching for a clustered file systems (CFS). The CFS manages access permissions to an entire space of the data segments by using the DSM module. In response to processing a request message from a remote DSM module to access one of the data segments, including in a response message permission to access the one of the data segments, and deciding if one of a transfer of ownership, and most recent contents of the one of the data segments should be included in the response message for the permission to access the one of the data segments. The last two components of the response message depend upon availability of the one of the data segments that is requested in a local external cache.