Technical Report CS0358

Title: The Private Workspace Model Feasibility and Applications to 2PL Performance Improvements
Authors: I. Gold, O. Shmueli and M. Hofri
Abstract: In the primitive workspace model of concurrency control the transaction management component of a database managemept system maintains a,private workspace for each transaction. Data items accessed by a transaction, regardless of the access mode, are cached in this workspace. At transaction commit time updates are made permanent in the database.

Two major advantages follow from the fact that writing of new values into the private workspace of the transactions do not affect the database state. First, the Concurrency Control has complete freedom in choosing how to synchronize conflicting transactions. Second, a trasaction restart may not cause cascading restarts.

One may suspect that it would be difficult to implement the private workspace idea in a real world database system. In this paper we show the feasibility of the model by introducing a parallel commit phase algorithm. By simulation experiments we show that system performance may be significantly improved by using a concurrency control method in which readers use certification, writers use 2PL and writers do not wait for readers.

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