
Database System Concepts
7th Edition
ISBN: 9780078022159
Author: Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher: McGraw-Hill Education
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Implement a system of three concurrent processes which read and write sequence numbers to a file. Each of the three processes must obtain 200 integers from the file. The file only holds one integer at a given time. Given a file, F, containing a single integer, each process must perform the following steps:
Please show steps and answer.

Transcribed Image Text:1. Open F
2. Read an integer N from the file
3. Close F
4. Output N and the process ID (PID) (either on the screen or an output file)
5. Increment N by 1
6. Open F
7. Write N to F (overwriting the current value in F)
8. Close F
Will the numbers that are read by the processes always be unique? Or do you observe duplicates of numbers being obtained by different processes?
That is, does a particular integer N appear in the output of more than one process?
Rewrite your implementation of these 3 processes to guarantee that no duplicate numbers are ever obtained by the processes. In other words, each
time the file is read by any process, that process reads a distinct integer. The processes must run concurrently.
Briefly describe why the code sequence above can lead to duplication of integer values and discuss how your solution will avoid these duplicates.
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