Systems, Methods, and Computer Program Products are provided for implementing transactional mechanisms by a plurality of procedures on data segments by using distributed shared memory (DSM) agents in a clustered file system (CFS). A new data segment is allocated and an associated cache data segment and metadata data segments, which are allocated for the new data segment and loaded into a cache and modified during the allocating of the new data segment, are added to a list of data segments modified within an associated transaction. The DSM agents assign an exclusive permission to the new data segment.