Both [[Red Hat]] and [[Oracle Corporation|Oracle]] have developed clustering software for [[Linux]].
[[OCFS|OCFS2]], the Oracle Cluster File System[http://oss.oracle.com/projects/ocfs2/] was added[<ref>http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=29552b1462799afbe02af035b243e97579d63350]</ref> to the official [[Linux kernel]] with version 2.6.16, in January 2006. The alpha-quality code warning on OCFS2 was removed in 2.6.19.
Red Hat's cluster software[http://sources.redhat.com/cluster/], including their [[Distributed lock manager|DLM[http://sources.redhat.com/cluster/dlm/]] and [[Global File System]] was officially added to the Linux kernel[ <ref>http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=1c1afa3c053d4ccdf44e5a4e159005cdfd48bfc6]</ref> with version 2.6.19, in November 2006.
Both systems use a DLM modeled on the venerable [[OpenVMS|VMS]] DLM.[<ref>http://lwn.net/Articles/137278/]</ref> Oracle's DLM has a simpler API. (the core function, <code>dlmlock()</code>, has eight parameters, whereas the VMS <small><code>SYS$ENQ</code></small> service and Red Hat's <tt>dlm_lock</tt> both have 11.)
