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數據庫代寫|Assignment代寫|sql代寫 - CSCI235/CSCI835 Database Systems Assignment 2
時間:2020-10-15
Scope This assignment includes the tasks related to database normalization, indexing of relational tables, and using cursors to search a database. The outcomes of the laboratory work are due by Saturday 17 October, 2020, 7.00 pm (sharp). Please read very carefully information listed below. This assignment contributes to 20% of the total evaluation in a subject CSCI235 and it contributes to 17% of the total evaluation in a subject CSCI835. A submission procedure is explained at the end of specification. This assignment consists of 4 tasks and specification of each task starts from a new page. It is recommended to solve the problems before attending the laboratory classes in order to efficiently use supervised laboratory time. A submission marked by Moodle as "late" is treated as a late submission no matter how many seconds it is late. A policy regarding late submissions is included in the subject outline. A submission of compressed files (zipped, gzipped, rared, tared, 7-zipped, lhzed, … etc) is not allowed. The compressed files will not be evaluated. All files left on Moodle in a state "Draft(not submitted)" will not be evaluated. An implementation that does not compile due to one or more syntactical and/or run time errors scores no marks. It is expected that all tasks included within Assignment 2 will be solved individually without any cooperation with the other students. If you have any doubts, questions, etc. please consult your lecturer or tutor during lab classes or office hours. Plagiarism will result in a FAIL grade being recorded for the assessment task. Task 1 (6 marks) Concurrent executions of database transactions Consider the database transactions listed below. T1 T2 T3 read(x) read(y) read(z) write(y,x+1) write(x,y+1) write(x,z+1) commit commit write(y,z+2) commit Assume that the initial values of the persistent data items x, y, and z are the following. x = 1, y = 2, and z= 3. (1) ( 2 marks) Show a sample concurrent execution of the transactions T1, T2, and T3 that is nonconflict serializable and that is view serializable. Prove, that the execution is nonconflict serializable and that it is view serializable. When visualizing the concurrent executions use a technique of two-dimensional diagrams presented to you during the lecture classes, for example, see a presentation 10 Introduction to Transaction Processing (1), slide 9. (2) (2 marks) Show a sample concurrent execution of the transactions T1, T2, and T3 that is conflict serializable and that is not order-preserving conflict serializable. Prove, that the execution is conflict serializable and that it is not order-preserving conflict serializable. When visualizing the concurrent executions use a technique of two-dimensional diagrams presented to you during the lecture classes, for example, see a presentation 10 Introduction to Transaction Processing (1), slide 9. (3) (2 marks) Show a sample concurrent execution of the transactions T1, T2, and T3 that is recoverable and that is not strict. Prove, that the execution is recoverable and that it is not strict. When visualizing the concurrent executions use a technique of two-dimensional diagrams presented to you during the lecture classes, for example, see a presentation 10 Introduction to Transaction Processing (1), slide 9. Deliverables A file solution1.pdf with: (1) a visualization of a sample concurrent execution of the transactions T1, T2, and T3 that is nonconflict serializable and that is view serializable and a proof that the execution is nonconflict serializable and that it is view serializable. (2) visualization of a sample concurrent execution of the transactions T1, T2, and T3 that is conflict serializable and that is not order-preserving conflict serializable and a proof that the execution is conflict serializable and that it is not order-preserving conflict serializable. (3) visualization of a sample concurrent execution of the transactions T1, T2, and T3 that is recoverable and that is not strict and a proof that the execution is recoverable and that it is not strict.

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