1. While users wereupdating the Premiere Products database, one of the transactions was interrupted.You need to explain to management what steps the DBMS will take to correct thedatabase. Using the sample log in Figure 7-11, list and describe the updatesthat the DBMS will roll back if transaction 2 is interrupted at 8:10.
The system started the transaction at 8:01 then added anorder at 8:02.. At that point, another two requests are included at 8:05 and8:09. Because transaction 2 was stopped at 8:10, while not forgetting that theend goal is to recover the correct data, the system needs to move back andremove the three order requests transactions. This activity allows the systemto recover the right data in the database.
2. Occasionally,users at Premiere Products obtain incorrect results when they run queries thatinclude built-in (aggregate, summary, or statistical) functions. The DBA toldmanagement that unrepeatable reads caused the problems. Use books, articles,and/or the Internet to research the unrepeatable read problem. Write a shortreport that explains the unrepeatable-read problem to management and use anexample with your explanation. (Note: Unrepeatable reads are also calledinconsistent retrievals, dirty reads, and inconsistent reads.)An unrepeatable read which is otherwise called a dirty reador inconsistent retrieval is more often than not happens when the recoverytransaction of any user read data which other users transactions have mostlyupdated.
For instance, for a situation where system needs to read thepay of three employees which brings the combined pay of $3,700, however anothertransaction of $300 a reward bonus which intended for the primary employee, butit was given to the third worker instead. The salary now becomes $1,600, $120and $1,200. The unrepeatable transaction happens if:a) The DBMS reads that the exchange was done by the firstuserb) The DBMS reads the first employee’s salary as $1,600 to$1,900 for second user’s transaction. c) The DMBS reads the second employee’s as $1,200 as firstuser’s transaction.d) The DBMS reads the third employee’s salary as $1,200 assecond user’s transactione) The DBMS reads the third employee’s salary as $1,200 asfirst user’s transaction.f) The DBMS reads the total employee’s salary as $4,700which exceeds the actual value.A mistake done by second user and the first user reads thepartial update, hence an unrepeatable transaction occurs.3.
You’ve explainedreplication to management, and some managers ask you for examples of whenreplication could be useful to them. Describe two situations, other than theones given in the text, when replication would be useful to an organization. Situation 1:The replicas are stored at locations in 4 countries namelyUSA, Canada, Australia and India. The companies operating center is accessingdata from replicas stored in USA. Suppose a hurricane hits USA and the datacenter is damaged. If the data is available at only that location, the companymay have to stop its operation until all the data has been recovered andrestored.
But here, the replicas of the same data are available at 3 locations.The company can access the data from a suitable location and can continue itsoperation without any delay. The company can continue can continue itsoperation as long as one remote location is up.
Situation 2:A query submitted at a site can be solved in parallel,suppose a request has come from a user that needs information from differentfiles in a database. It this scheme, replicas of database are available atdifferent locations. So, the query can process faster compared to a querysubmitted at a centralized system.4. The staff of themarketing department at Premiere Products is scheduled to receive somestatistical databases, and they need you to explain these databases to them. (Astatistical database is a database that is intended to supply only statisticalinformation to users; a census database is an example of a statisticaldatabase.) Using a statistical database, users should not be able to inferinformation about any individual record in the database. Use books, articles,and/or the Internet to research statistical databases; then write a report thatexplains them, discusses the problem with using them, and gives the solution tothe problem.
Statistical Databases:Are different from conventional DBMS, a statistical DBMS(SDMS) helps to model store and manipulate data in a way helpful for otherusers to perform statistical analyses of data. It is Online AnalyticalProcessing (OLAP) Example is the database for analyzing the informationcollected in census. Requirements of Statistical Database:Statistical database involves data and queries from datadifferent fields like biology physics etc.So, statistical database have additional requirementscompared to the conventional DBMS.These are listed below:Data Model: A relational model used in conventional DBMS isnot sufficient for statistical databases. Data models that support complexnature of data are needed in statistical database.
Query Language: A statistical database is from differentdisciplines and requires specialized operations.Concurrency control:Statistical database applications do not have strict concurrency controlmechanisms compared to conventional database.Integrity Constraints: Statistical database results incomplex constraints and these have to be expressed in SDMS.Recovery: Instatistical databases mechanisms for recovering log transactions are needed.Physical Database Organization: Statistical databases needoptions for efficient physical organization of data.
Data Analysis Requirements: Most important need ofStatistical database is the tools for analyzing and manipulating data.Problems in Statistical Database:Statistical database has security issues. By answeringcertain queries, sensitive information may be leaked.Some common solutions are:Allowing only aggregate queries like SUM, COUNT, AVG etc.
Don’t return exact values of a query but a range of valuesto be returned like exact income.Selective WHERE clauses to be restricted.All queries should be subjected to auditing in order toidentify improper users.5. The DBA atPremiere Products wants you to investigate biometric identification techniquesfor potential use at the company for computer authentication purposes.
Usebooks, articles, and/or the Internet to research these techniques, then write areport that describes the advantages and disadvantages of each of thesetechniques. In addition, recommend one technique and provide a justificationfor your recommendation.There are two phases in Biometric systems Enrollment and Verification.During enrollment the user’s data is extracted and stored in a database. Thefirst step in acquiring user information is physical measurement of the userdata and extracting the features from measurement. This extracted feature isknown as a template and template is stored in the database.
During verificationusers features is again extracted to form template. This template is matchedwith stored template and a matching score is generated. Depending on thematching score the system ma kes a decision to accept or reject that person.
Biometric Techniques:• Fingerprint• iris, • voice, Fingerprint:Technology is widely used and is well accepted.Advantages: Levelof accuracy is high, it can be deployed in a wide range of environment, thesedevices are ergonomic and easy to use, and more than one finger can beenrolled.Disadvantages:Some ae unable to enroll, finger prints may deteriorate over time, some are notwilling to provide finger prints as it is associated with forensicapplications. Face Recognition:Technology uses images form camera to recognize a person. Applications for facematching include Identification, Surveillance, Monitoring, and Fraud PreventionAdvantages:Existing devices like camera can be used to capture user images, user imagescan be taken without direct physical contact, and static images as well asmoving images can be taken. Disadvantages: Face change over time, thus reducing matchingaccuracy. The privacy of individual comes into question.Iris Scan Technology:Most safe and accurate biometric system available.
Advantages: Thistechnology reduces false matching; Iris characteristic is stable over lifetime. Disadvantages:Can encounter difficulty using this technology, initial scans must be obtainedfor technology to work. Users may feel uneasiness as it is an eye basedtechnology and will need special devices for iris images.
Voice Recognition:is difficult from speech recognition. It is actually speaker recognition. Advantages:Software has the ability to learn and recognize a unique speech patterns.Disadvantages:Accuracy is dependent on capturing device and surrounding noise it also has lowaccuracy.
You must speak clearly for the software to work. If the user has runswords together, or mumbles, the recognition process may take longer. Somepunctuation must be dictated.Finger print recognition is recommended technology becauseit is widely accepted as the major means of human identification.