Modern Database Management
13th Edition
ISBN: 9780134773650
Author: Hoffer
Publisher: PEARSON
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Chapter 7, Problem 7.22PAE
Program Plan Intro
a. The balance that will be included for the customer after the last transaction was completed.
Program Plan Intro
b. Correct balance included for the customer after three transactions have been processed.
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Database Systems
Each branch of the Jaja restaurant has a mainstay menu that is very popular with customers, so information on the availability of the number of servings is needed to be able to serve orders. Here are two transactions that are ordering a food menu at the same time.
T1: Start the transaction at time t1, read 10 servings of food stock at t2. Because ordering one portion, the stock is reduced by 1 at t3. On t6, update the stock count, and commit to t7.
T2: Transaction T2 starts a transaction on t2, reads the number of stocks in t3 as many as 10. At t4 orders 3 portions. On t5 it updates the stock to 7 and then on t6 commits it.
As a result of the T1 and T2 transactions above, there was an error in the amount of food stocks. Make a solution with 2PL. What kinds of problems happened? Give a reason why choosing this type of problem! How much food is still available?
In the problem below, x and y are local application program values Read( ) and Writel ) 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 nart the transactions are operating with isolation level READ UNCOMMITTED (no locks)
Time
Transaction 1
Transaction 2
Read(y)
y=y+5
2
Read(y)
y=y+ 10
3
4
Write(y)
Read(x)
7
Read(x)
8
X=x+ y:
Write(y)
Commit
9.
10
11
x=x+y
Write(y)
12
13
Commit
For 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 concurrency
problems of this type for…
To access a database, we need to open a connection to it first and close it once our job is done. Connecting to a database depends on the type of the target database and the database management system (DBMS). For example, connecting to a SQL Server database is different from connecting to an Oracle database. But both these connections have a few things in common: •They have a connection string •They can be opened•They can be closed•They may have a timeout attribute (so if the connection could not be opened within the timeout, an exception will be thrown).Your job is to represent these commonalities in a base class called DbConnection. This class should have two properties: ConnectionString : stringTimeout : TimeSpanA DbConnection will not be in a valid state if it doesn’t have a connection string. So you need to pass a connection string in the constructor of this class. Also, take into account the scenarios where null or an empty string is sent as the connection string. Make sure to…
Chapter 7 Solutions
Modern Database Management
Ch. 7 - Prob. 7.1RQCh. 7 - Prob. 7.2RQCh. 7 - Prob. 7.3RQCh. 7 - Prob. 7.4RQCh. 7 - Describe the advantages and disadvantages of...Ch. 7 - Describe the common components needed to create a...Ch. 7 - What are the six common steps needed to access...Ch. 7 - Prob. 7.8RQCh. 7 - Prob. 7.9RQCh. 7 - Prob. 7.10PAE
Ch. 7 - Prob. 7.11PAECh. 7 - Prob. 7.12PAECh. 7 - Prob. 7.13PAECh. 7 - Find some dynamic Web site code, such as that...Ch. 7 - Prob. 7.15PAECh. 7 - Prob. 7.16PAECh. 7 - Prob. 7.17PAECh. 7 - Consider the example code shown in Figure 7-10....Ch. 7 - Prob. 7.19PAECh. 7 - Prob. 7.20PAECh. 7 - Prob. 7.21PAECh. 7 - Prob. 7.22PAECh. 7 - Prob. 7.23PAECh. 7 - Prob. 7.24PAE
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