trogers@yosemite.Eng.Sun.COM (Tom Rogers - Database Engineering) (10/19/90)
>The idea of using predicate locks for database concurrency control >has been around for over ten years. But still there are not many >commercial systems which use predicate locking as a primary method >for concurrency control. >My question is the following: Are there really no commercial systems >that use predicate locking ? Predicate locking has been around in a commercial database system for well over 10 years. Check out HP's IMAGE 3000. At some point testing for arbitrarily complex predicates becomes extremely expensive, and implementors have found that row and page level locking is superior in terms of ease of implementation and speed.