TAL Distributors Exercises For the following exercises, you will address problem
ID: 652530 • Letter: T
Question
TAL Distributors Exercises
For the following exercises, you will address problems and answer questions from management at TAL Distributors.
You do not use the TAL Distributors database for any of these exercises.
1. While users were updating the TAL Distributors database, one of the transactions was interrupted. You need to
explain to management what steps the DBMS will take to correct the database. Using the sample log shown in
Figure 7-11, list and describe the updates that the DBMS will roll back if transaction 2 is interrupted at 8:10.
Explanation / Answer
In a DBMS , while storing the data , there are the possibilities that some how data can be damaged or destroyed . A DBMS must have the process to do the recovery to such destroy and damage as damaged data can cause inconsistency or invalid data to the database .To recover this damage , the database must return to the last correct value . This process is known as the recovery process of the database.
According to the question , when the user was updating the premier products database , one of the transaction was interrupted. The interrupted transaction is transaction 2 which is interrupted at 8:10 . According to the table , the DBMS started the transaction at 8:01 and added an order 8:02. Then another two orders are added at 8:05 and 8:09 . As a transaction 2 is interrupted at 8:10. Hence in order to recover the correct data , the DBMS has to rollback and delete the three added orders. Though this rollback action, the DBMS can recover the correct data in the database.
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