INTER-SYSTEM LOCK MANAGEMENT WITHIN SINGLE REQUEST BONDS
Original Publication Date: 2001-May-01
Included in the Prior Art Database: 2003-Jun-18
Limiting a lock manager for a subsystem to a single held lock indicator and a single pending request per lockable resource introduces problems that do not exist if the lock manager can have multiple requests per resource. Examples of these problems are resource starvation due to unfair inter-sytem lock processing, and deadlocks exclusively caused by the lock manager. Disclosed is a system that eliminates these problems through a combination of contention indicators, time-stamps, and careful use of the pending request. The notion of a held composite state is introduced. The held composite state is defined as the most restrictive state of the locks held on the resource by a given lock manager assuming the locks were all owned by the same unit of work. The notion of a requested composite state is introduced. The requested composite state is defined as the held composite state of a resource if the highest priority waiting request were granted. The notion of a contention marker is introduced. A contention marker indicateds intersystem contention exists for a resource.