2-version 2PL (1) Adjustments to 2PL:
{"Image DocumentName": "2-version 2PL (1) Adjustments to 2PL:", "Image ImageDescription": "2PL: A wl lock is exclusive. In particular, it prohibits concurrent reads. By using two versions we wish to relax the condition. If ti writes x: a new version xi is created; a lock must be found for x that inhibits reads on xi and the creation of further versions for x (2-version 2PL!), and allows other transactions to read the single old x. On commit of ti xi becomes the current version and the old version of x becomes inaccessible. Conclusion: Use 2PL for ww synchronization, and version selection f\u00fcr rw synchronization.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}