Rapid transaction-undo recovery using twin-page storage management

A twin-page storage method, which is an alternative to the TWIST (twin slot) approach by A. Reuter (190) for rapid transaction-undo recovery is presented. In contrast to TWIST, the twin-page approach allows dirty pages in the buffer to be written at any instant onto a disk without the requirement of undo logging, and, when a transaction is aborted, no explicit undo is required. As a result, all locks accumulated by the aborted transaction can be released earlier, allowing other transactions waiting for the locks to proceed. Through maintenance of aborted transaction identifiers, invalid pages written by the aborted transaction coexist with other valid pages and are guaranteed not to be accessed by subsequent transactions. Instead of an explicit undo, most of the invalid pages are overwritten by subsequent normal updates. Performance in terms of disk I/O and CPU overhead for transaction-undo recovery is analyzed and compared with TWIST. It is shown that the presented method is particularly suited for applications where there are a large number of updates written onto disk when transactions are aborted, and there are frequent aborts