Chapter 13: Problem 13
How does double buffering improve block access time?
Short Answer
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Chapter 13: Problem 13
How does double buffering improve block access time?
These are the key concepts you need to understand to accurately answer the question.
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Get started for freeSuppose we have a sequential (ordered) file of 100,000 records where each record is 240 bytes. Assume that \(B=2400\) bytes, \(s=16 \mathrm{ms}, r d=8.3 \mathrm{ms},\) and \(b t t=0.8 \mathrm{ms}\) Suppose we want to make \(X\) independent random record reads from the file. We could make \(X\) random block reads or we could perform one exhaustive read of the entire file looking for those \(X\) records. The question is to decide when it would be more efficient to perform one exhaustive read of the entire file than to perform \(x\) individual random reads. That is, what is the value for \(X\) when an exhaustive read of the file is more efficient than random \(X\) reads? Develop this as a function of \(X\)
Discuss the techniques for allowing a hash file to expand and shrink dynamically. What are the advantages and disadvantages of each?
Suppose that we have an unordered file of fixed-length records that uses an unspanned record organization. Outline algorithms for insertion, deletion, and modification of a file record. State any assumptions you make.
Suppose that a file initially contains \(r=120,000\) records of \(R=200\) bytes each in an unsorted (heap) file. The block size \(B=2400\) bytes, the average seek time \(s=\) \(16 \mathrm{ms}\), the average rotational latency \(r d=8.3 \mathrm{ms}\) and the block transfer time \(b t t=\) \(0.8 \mathrm{ms} .\) Assume that 1 record is deleted for every 2 records added until the total number of active records is 240,000 a. How many block transfers are needed to reorganize the file? b. How long does it take to find a record right before reorganization? c. How long does it take to find a record right after reorganization?
Why is accessing a disk block expensive? Discuss the time components involved in accessing a disk block.
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