Holding a Page: Enhanced Page Level Access Control for Database Systems

A new scheme for physically accessing tuples by multiple transactions is described for database systems using a shared memory buuer cache. Using this scheme, a transaction must rst obtain logical permission to access a tuple, for example, by taking a lock on the tuple. Once logical permission has been granted, a page level latch is taken for the initial physical access to the tuple. However, by the introduction of a new primitive, hold, into the latching system which ensures that the tuple is not moved, a latch on the page is not required to subsequently read the tuple. This brings the physical level of concurrency closer to the logical level of concurrency. Our scheme is compared with other schemes which can be used for access control.