TAILIEUCHUNG - Concurrency Control in Distributed Database Systems

When you create a geodatabase, as you did in Exercise Add a database server to the Catalog tree and create a geodatabase, there is no data in it. You must add data to new geodatabases either by creating new datasets, importing data, or copying data from one geodatabase and pasting it into another. In this exercise, you will create a feature dataset, then import data from a personal geodatabase to populate it. You will also copy data from a file geodatabase and paste it into your new geodatabase. After the data is loaded, you will update the database statistics | Concurrency Control in Distributed Database Systems PHILIP A. BERNSTEIN AND NATHAN GOODMAN Computer Corporation of America Cambridge Massachusetts 02139 In this paper we survey consolidate and present the state of the art in distributed database concurrency control. The heart of our analysis is a decomposition of the concurrency control problem into two major subproblems read-write and write-write synchronization. We describe a senes of synchronization techniques for solving each subproblem and show how to combine these techniques into algorithms for solving the entire concurrency control problem. Such algorithms are called concurrency control methods. We describe 48 principal methods including all practical algorithms that have appeared m the literature plus several new ones. We concentrate on the structure and correctness of concurrency control algorithms. Issues of performance are given only secondary treatment. Keywords and Phrases concurrency control deadlock distributed database management systems locking serializability synchronization timestamp ordering timestamps two-phase commit two-phase locking CR Categories INTRODUCTION The Concurrency Control Problem Concurrency control is the activity of coordinating concurrent accesses to a database in a multiuser database management system DBMS . Concurrency control permits users to access a database in a multiprogrammed fashion while preserving the illusion that each user is executing alone on a dedicated system. The main technical difficulty in attaining this goal is to prevent database updates performed by one user from interfering with database retrievals and updates performed by another. The concurrency control problem is exacerbated in a distributed DBMS DDBMS because 1 users may access data stored in many different computers in a distributed system and 2 a concurrency control mechanism at one computer cannot instantaneously know about interactions at other computers. Concurrency control has been .

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