Consider a database system that includes an atomic increment operation, inaddition to the read and write operations. Let V be the value of data item X.The operationincrement(X) by C sets the value of X to V + C in an atomic step. The value of X is not availableto the transaction unless the latter executes a read(X).Assume that increment operations lock the item in increment mode using thecompatibility matrix in Figure 18.25.a. Show that, if all transactions lock the data that they access in the correspondingmode, then two-phase locking ensures serializability.b. Show that the inclusion of increment mode locks allows for increasedconcurrency.
Consider a database system that includes an atomic increment operation, inaddition to the read and write operations. Let V be the value of data item X.The operationincrement(X) by C sets the value of X to V + C in an atomic step. The value of X is not availableto the transaction unless the latter executes a read(X).Assume that increment operations lock the item in increment mode using thecompatibility matrix in Figure 18.25.a. Show that, if all transactions lock the data that they access in the correspondingmode, then two-phase locking ensures serializability.b. Show that the inclusion of increment mode locks allows for increasedconcurrency.
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
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| Consider a addition to the read and write operations. Let V be the value of data item X. The operation increment(X) by C sets the value of X to V + C in an atomic step. The value of X is not available to the transaction unless the latter executes a read(X). Assume that increment operations lock the item in increment mode using the compatibility matrix in Figure 18.25. a. Show that, if all transactions lock the data that they access in the corresponding mode, then two-phase locking ensures serializability. b. Show that the inclusion of increment mode locks allows for increased concurrency. |
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