1. Andy02/18/2006 16:11:10
Homepage: http://jboss.org/jbossBlog/blog/acoliver/

actually in theory DB2 style (I call "old style") locking is less expensive than MVCC. Making a copy is more expensive. However in concurrency sometimes doing the more expensive thing increased perceieved perforamance. Think of a car wash. If I only staff one car line then my costs are lower and I theoretically will make more profit right? However, if the line is 2x longer and everyone sees this and leaves (timeout) while waiting then it won't be. Same general concept. Using more resources for the more expensive concurrent lock gives you better performance. However many developers don't know how to use MVCC anyhow and end up doing select for update everywhere and getting DB2 style locking anyhow....