The M Lock Utility (LKE) is a tool used for examining and changing the GT.M LOCK environment. In M, the LOCK command reserves one or more resource names. Only one process at a time can reserve a resource name. M code commonly uses LOCKs as flags that control access to global data. Generally, a LOCK specifies the resource with the same name as the global variable that requires protected access. However, this is only a convention.

LOCKing does not keep two or more processes from modifying the same global variable. It only keeps another process from LOCKing the same resource name at the same time.