Oracle International Corporation

Sherry Listgarten

Sanjay Verma

Sibsankar Haldar

Chi-Kim Hoang

Mark L McAuliffe

Mark L Mcauliffe

A two copy versioning scheme is proposed. The scheme provides efficient implementation for a high read load database and eliminates read dependencies. The versioning scheme provides efficient implementation for transactions executing under ANSI READ COMMITTED isolation, and is extensible to serializable isolation. The two-copy versioning scheme is garbage free meaning that all versions of data records are used during execution and is adapted to index scanning operations. A 'deferred delete' scheme allows read transactions to complete data deallocation operations. Statements that require 'snapshots' are efficiently supported.

Database management system with efficient version control

New lock modes are based on the concept of neighborhoods and are applied to spaces in indexes. The new lock modes include a Read, or shared, neighborhood (Snei) lock mode and a Write neighborhood (Xnei) that enhance concurrency among non-serializable transactions.

Neighboring locking technique for increasing concurrency among transactions

Activity Duration Locking (ADL) provides an efficient simple solution to manage a potentially large number of concurrently active lock groups. The ADL scheme allows a transaction fine control over creation of lock groups and classification of locks into lock groups enabling faster releasing of locks in groups. The life time that the lock group is active defines a new lock duration. This allows a large number of lock durations to be defined with the creation of each new lock group and any number of lock durations can be active for a given transaction. A very general concept of lock duration is supported without using any a priori semantics to individual lock durations and the duration of a lock group may be determined by the transaction as desired.

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Palo Alto, CA, United States of America

Sherry Listgarten