(a) Locking-based algorithms for concurrency control can be employed to synchronize the execution of transactions. Explain what is meant by a serializable schedule and show that the following locking-based schedule is not serializable: S = [wlS1U1B11S1U1B0(y), wlS1U1B12S1U1B0(y), RS1U1B11S1U1B0(y), WS1U1B11S1U1B0(y), RS1U1B12S1U1B0(y), WS1U1B12S1U1B0(y), rlS1U1B11S1U1B0(y), rlS1U1B12S1U1B0(y), wlS1U1B12S1U1B0(z), RS1U1B12S1U1B0(z), WS1U1B12S1U1B0(z), rlS1U1B12S1U1B0(z), CS1U1B12S1U1B0, wlS1U1B11S1U1B0(z), RS1U1B11S1U1B0(z), WS1U1B11S1U1B0(z), rlS1U1B11S1U1B0(z), CS1U1B11S1U1B0] where RS1U1B1iS1U1B0(x)/WS1U1B1iS1U1B0(x) indicates a read/write by transaction i on data item x rlS1U1B1iS1U1B0(x)/wlS1U1B1iS1U1B0(x) indicates a release/write lock by transaction i on item x CS1U1B1iS1U1B0 indicates a commit operation by transaction i. (b) Identify the problem with the above schedule, and produce a correct locking-based serializable schedule.

(a) A schedule S is said to be serializa

Exam 7: Security, Administration and Transaction Management

The locking information for several transactions is shown in Table 2. Produce a wait-for-graph (WFG) for the transactions and determine whether deadlock exists.

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Question 1

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WFG will show that system is in deadlock.

Locking-based algorithms for concurrency control can be employed to synchronize the execution of transactions. Explain the rules for two-phase locking in a centralized Database Management System and why each of these is necessary to avoid the database becoming inconsistent.

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Question 2

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See Section 22.2.3.

Discuss the problems associated with microcomputer security, and contrast the measures required to provide a secure environment with those of a mainframe computing environment.

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The problems concern data security and physical security. Problems and precautions in dealing with these are generally as for part two of the previous question. It is important that a contrast is made with a mainframe environment. For example, in dealing with microcomputers, you are dealing with individual machines and staff, possibly over a wide location. Much of the responsibility rests with members of staff, consequently, all staff training is important. In the mainframe environment it is possible to set up centralized controls (physical and logical). Consequently, it should be an easier environment to control, with the responsibility residing in the IT manager.

(a) Locking-based algorithms for concurrency control can be employed to synchronize the execution of transactions. Explain what is meant by a serializable schedule and show that the following locking-based schedule is not serializable: S = [wl₁(y), wl₂(y), R₁(y), W₁(y), R₂(y), W₂(y), rl₁(y), rl₂(y), wl₂(z), R₂(z), W₂(z), rl₂(z), C₂, wl₁(z), R₁(z), W₁(z), rl₁(z), C₁] where R_i(x)/W_i(x) indicates a read/write by transaction i on data item x rl_i(x)/wl_i(x) indicates a release/write lock by transaction i on item x C_i indicates a commit operation by transaction i. (b) Identify the problem with the above schedule, and produce a correct locking-based serializable schedule.

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Question 4

Detail the types of problems associated with microcomputer security and the types of countermeasures that could be installed against loss.

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Question 5

A taxonomy of concurrency control algorithms can classify algorithms as pessimistic or optimistic. Compare and contrast these algorithms.

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Question 6

Explain the integrity features that a database management system may provide making reference to the system used, and indicate the disadvantages that arise where they are not available.

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Question 7

'One of the potential advantages of Distributed Database Management Systems is improved reliability and availability.' (a) The consistency and reliability aspects of transactions are due to the 'ACIDity' properties of transactions. Discuss each of these properties and how they relate to the concurrency control and recovery mechanisms. Give examples to illustrate your answer.

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Question 8

(a) Produce a wait-for-graph for the transactions with locking information shown in Table 1. What can you conclude for this graph? (b) Compare and contrast the approaches to deadlock management in database systems.

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Question 9

The increasing accessibility of databases on the Internet and intranets requires a reanalysis and extension of the normal approaches to security. Discuss some of the issues associated with the database system security in these environments.

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Question 10

Discuss the types of threat that might occur within the general database environment, and indicate the measures that could be taken to safeguard against them.

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Question 11

Describe a general plan of action for initiating a security policy, elaborating on each stage that might be undertaken.

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Question 12

Showing 1 - 12 of 12

The locking information for several transactions is shown in Table 2. Produce a wait-for-graph (WFG) for the transactions and determine whether deadlock exists.

Locking-based algorithms for concurrency control can be employed to synchronize the execution of transactions. Explain the rules for two-phase locking in a centralized Database Management System and why each of these is necessary to avoid the database becoming inconsistent.

Discuss the problems associated with microcomputer security, and contrast the measures required to provide a secure environment with those of a mainframe computing environment.

Detail the types of problems associated with microcomputer security and the types of countermeasures that could be installed against loss.

A taxonomy of concurrency control algorithms can classify algorithms as pessimistic or optimistic. Compare and contrast these algorithms.

Explain the integrity features that a database management system may provide making reference to the system used, and indicate the disadvantages that arise where they are not available.

(a) Produce a wait-for-graph for the transactions with locking information shown in Table 1. What can you conclude for this graph? (b) Compare and contrast the approaches to deadlock management in database systems.

The increasing accessibility of databases on the Internet and intranets requires a reanalysis and extension of the normal approaches to security. Discuss some of the issues associated with the database system security in these environments.

Discuss the types of threat that might occur within the general database environment, and indicate the measures that could be taken to safeguard against them.

Describe a general plan of action for initiating a security policy, elaborating on each stage that might be undertaken.

Introduction to Databases and Database Environment

The Relational Model, Relational Algebra and Relational Calculus

SQL: Data Manipulation and Advanced SQL

Object-Relational DBMSs, Database Planning, Design, and Administration

Entity-Relationship Modeling and Normalization

Methodology-Conceptual Database Design and Methodology-Physical Database Design for Relational Databases

Query Processing

Distributed DBMSs Concepts and Design

Distributed DBMSs-Advanced Concepts and Object-Oriented DBMSs-Concepts and Design

Object-Oriented DBMSs-Standards and Systems

Web Technology and DBMSs, Semistructured Data and XML and Data Warehousing Concepts

Data Warehousing Design

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