Operating systems use lock managers to organise and serialise the access to resources.
In this way a DLM provides software applications which are distributed across a cluster on multiple machines with a means to synchronize their accesses to shared resources.
The main performance benefit comes from solving the problem of disk cache coherency between participating computers.
This can relate to a file, a record, an area of shared memory, or anything else that the application designer chooses.
The original process can then optionally take action to allow the other access (e.g. by demoting or releasing the lock).
OCFS2, the Oracle Cluster File System was added[2] to the official Linux kernel with version 2.6.16, in January 2006.
Red Hat's cluster software, including their DLM and GFS2 was officially added to the Linux kernel [3] with version 2.6.19, in November 2006.
(the core function, dlmlock(), has eight parameters, whereas the VMS SYS$ENQ service and Red Hat's dlm_lock both have 11.)