Suppose that a DBMS recognizes increment, which increments an in- teger-valued object by 1, and decrement as actions, in addition to reads and writes. A transaction that increments an object need not know the value of the object; incre- ment and decrement are versions of blind writes. In addition to shared and exclusive locks, two special locks are supported: An object must be locked in I mode before incrementing it and locked in D mode before decrementing it. An I lock is compatible with another I or D lock on the same object, but not with S and X locks. 1. Illustrate how the use of I and D locks can increase concurrency. (Show a schedule allowed by Strict 2PL that only uses S and X locks. Explain how the use of I and D locks can allow more actions to be interleaved, while continuing to follow Strict 2PL.) 2. Informally explain how Strict 2PL guarantees serializability even in the presence of I and D locks. (Identify which pairs of actions conflict, in the sense that their relative order can affect the result, and show that the use of S, X, I, and D locks according to Strict 2PL orders all conflicting pairs of actions to be the same as the order in some serial schedule.)

Suppose that a DBMS recognizes increment, which increments an in- teger-valued object by 1, and decrement as actions, in addition to reads and writes. A transaction that increments an object need not know the value of the object; incre- ment and decrement are versions of blind writes. In addition to shared and exclusive locks, two special locks are supported: An object must be locked in I mode before incrementing it and locked in D mode before decrementing it. An I lock is compatible with another I or D lock on the same object, but not with S and X locks. 1. Illustrate how the use of I and D locks can increase concurrency. (Show a schedule allowed by Strict 2PL that only uses S and X locks. Explain how the use of I and D locks can allow more actions to be interleaved, while continuing to follow Strict 2PL.) 2. Informally explain how Strict 2PL guarantees serializability even in the presence of I and D locks. (Identify which pairs of actions conflict, in the sense that their relative order can affect the result, and show that the use of S, X, I, and D locks according to Strict 2PL orders all conflicting pairs of actions to be the same as the order in some serial schedule.)

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

See similar textbooks

Similar questions

1. When dose buffer overflows occur Buffer overflows occurs when we do not properly account for the size of the data input into an application. When there is an escalation of privilege in an application When there is no appropriate authentication mechanism When authorization is not implemented on a given application.
Explain the distinction between an explicit and an implicit lock.
If multiple threads are acquiring multiple locks, the order in which the threads attempt to acquire them makes no difference. True or False
48. Which of the following is not a property of a transaction? a. Atomicity b. Simplicity c. Isolation d. Durability
What is "two-phase locking" and how does it ensure serializability?
Here is a list of the various database encryption configurations that can be applied.
87. The property of transaction that persists all the crashes is a. Atomicity b. Durability c. Isolation d. All of the mentioned
I found this question in one book, Im not able to solve it, help me
TASK 2 Write an anonymous block that demonstrates the use of a predefined Oracle server exception when an attempt is made to select all employees from the EMP who have a NULL department number.
If a branch separates all records into a single class, then the purity is very low. True False
A new timestamp is given to a transaction when it is rolled back using timestamp ordering. Why can't it just preserve the previous timestamp?
After getting a job going on a database, you can use either a trigger or a process. When should a gun be pulled? What are they?