الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 148 |  |  |
| | | from | 148 | | |
Abstract
In this thesis an algorithm is proposed for
concurrency control in distributed databases . The algorithm
uses the optimistic technique for r-w synchronization ,
Thomas write rule (TWR) for w-w synchronization and the
locking to minimize the no of restarts.
The proposed algorithm combines these techniques in
such a way to have the advantages of each one , namely the
excellent performance of the optimistic technique in low
arrival rate and read oriented environment , the advantages
of TWR in w-w synchronization and the small no of restarts
caused by locking technique.
Two interfaces are built to interface optimistic
technique with TWR and locking techniques. The interfaces
introduce one additional set called validate set and two
extra tables Read lock table and Write lock table to the
original optimistic technique. The validate set is used to
overcome the effect of the proposed move of the transaction
number from the end of write phase to the end of the
validation phase. The two locking tables are used to lock
the database elements read or written by transaction
restarted two times.
The algorithm is presented in details , the correctness