In the problem below, x and y are local application program values Read( ) and Writel ) fetch and stored thepersistent values in a database. The database values are read / written by two different transactions. The timesequence of these operations is shown in the table below. You cannot change the time sequence.Take the initial values of x and y to be x = 4, y = 2.a) In this nart the transactions are operating with isolation level READ UNCOMMITTED (no locks)TimeTransaction 1Transaction 2Read(y)y=y+52Read(y)y=y+ 1034Write(y)Read(x)7Read(x)8X=x+ y:Write(y)Commit9.1011x=x+yWrite(y)1213CommitFor the execution order shown above, what are the final values of x and y?Answer: x=b) There is a problem with the interleaved execution plan for these transactions.What is the problem, i.e., which concurrency problem does this demonstrate?Answer:c) Rewrite the sequence of operations using the standard technique for dealing with concurrencyproblems of this type for isolation level SERIALIZABLE. In the columns on the right specifythe type of requests made. (type your answer into the grid below) You cannot change the time sequence.TimeTrans # RequestsTransaction 1Transaction 2123456.7910111213d) Was the concurrency problem completely solved? If not, what happened and what should be done next?Answer:

NOTE: According to the rules, the first 3 questions are answerable. Given, T1 T2 R(y)…

In the problem below, x and y are local application program values Read( ) and Write( ) fetch and stored the persistent values in a database, The database values are read / written by two different transactions. The time sequence of these operations is shown in the table below. You cannot change the time sequence. Take the initial values of x and y to be x = 4, y = 2. a) In this part the transactions are operating with isolation level READ UNCOMMITTED (no locks) Time | Transaction 1 Transaction 2 Read(y) y=y+5 Read(y) yy+ 10 3 Write(y) Read(x) 6. Read(x) X=x+ y: Write(y) 8. 10 Commit 11 Xx+y Write(y) Commit 12 13 For the execution order shown above, what are the final values of x and y? Answer: x=

In the problem below, x and y are local application program values Read( ) and Write( ) fetch and stored the persistent values in a database, The database values are read / written by two different transactions. The time sequence of these operations is shown in the table below. You cannot change the time sequence. Take the initial values of x and y to be x = 4, y = 2. a) In this part the transactions are operating with isolation level READ UNCOMMITTED (no locks) Time | Transaction 1 Transaction 2 Read(y) y=y+5 Read(y) yy+ 10 3 Write(y) Read(x) 6. Read(x) X=x+ y: Write(y) 8. 10 Commit 11 Xx+y Write(y) Commit 12 13 For the execution order shown above, what are the final values of x and y? Answer: x=

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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62 Consider a bank database with snapshot isolation. Describe a situation in which a non-serializable execution causes an issue for the bank.
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Explain the concept of versioning in object serialization and how it helps maintain compatibility between different versions of serialized objects.
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Transactions often take a very long time to finish when an optimistic approach to concurrency management is used. Explain.
A taxi company would like to provide an online service for customers to book a trip and for taxi drivers to check their upcoming trips. A database needs to be created to store customer data (name, address, email, telephone number) and trip information (pick up and drop off address and pick up time and date). Furthermore, your database should contain driver information (name and license plate). Each trip must be assigned to exactly one driver (and trips for a driver must not overlap). Customers who are not registered yet need to register (providing their address, phone number, email address, and credit card information). A registered customer should be able to book a trip, i.e. provide the pick-up address and time as well as the drop-off address via a graphical user interface. Customers should also be able to view their trips and cancel them if needed. All these operations are only possible after a customer signs in (which means they must be registered). Each new trip must be confirmed…
Subject :database
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