HYBRID MEMORY ACCESS PROTOCOL FOR SERVICING MEMORY ACCESS REQUEST BY ASCERTAINING WHETHER THE MEMORY BLOCK IS CURRENTLY CACHED IN DETERMINING WHICH PROTOCOLS TO BE USED

A method, in a computer network having a first plurality of nodes coupled to a common network infrastructure and a distributed shared memory distributed among the first plurality of nodes, for servicing a memory access request by a first node of the first plurality of nodes. The memory access request pertains to a memory block of a memory module that has a home node different from the first node in the computer network. The home node has a partial directory cache that has fewer directory cache entries than a total number of memory blocks in the memory module. The method includes the step of ascertaining whether the memory block is currently cached in the partial directory cache. If the memory block is currently cached in the partial directory cache, the first memory access request is serviced using a directory protocol. If the memory block is not currently cached in the partial directory cache, the first memory access request is serviced using a directory-less protocol. The directory states pertaining to copies of the memory block in the network nodes is cached in the partial directory cache when the memory access request generates a renewal point with respect to the directory states.