Patent ID: 8463829

Claim:
A method 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) using a processor device, the method comprising: allocating a new data segment and adding 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, to a list of data segments modified within an associated transaction, wherein the DSM agents assigns an exclusive permission on the new data segment; and retrieving a disk data segment for usage by examining the cache for the presence of a cache data segment associated with the disk data segment; wherein if the disk data segment is not associated with the cache data segment: associating the cache data segment with the disk data segment, wherein if the cache data segment is associated with the disk data segment: creating a shadow data segment in the cache for a node if the cache data segment is currently being written to a final storage location with an asynchronous checkpoint operation and the node requires exclusive permission on the disk data segment, and upon completion of the asynchronous checkpoint operation: disassociating the cache data segment from the disk data segment, wherein the shadow data segment is a sole representation of the disk data segment within the cache, and acquiring permission on the disk data segment via one of the DSM agents according to a request by the node for one of exclusive and shared permission.