CS157b Spring 2020Practice Midterm

Due to the coronavirus the midterm will be online and open book/internet. That said, you will be on the honor system not to communicate with other members of the class or internet community about problems on the test. I will give 24 hours from when I post the test to complete it. If you have a correctly filed AEC accommodation and need more time please send me an email.

To study for the midterm I would suggest you:

• Start early and allow you self more than one day for study.
• Keep the bar to study low, if you have spare time, while doing something else, flip through your notes.
• Know how to do (by heart) all the practice problems.
• Go over your notes at least three times. On the second and third time try to see how much you can remember from the first time.
• Go over the homework problems.
• Try to create your own problems similar to the ones I have given and solve them.
• Skim the relevant sections from the book.
• If you want to study in groups, at this point you are ready to quiz each other.

The practice midterm is below.

1. Draw a diagram of the memory hierarchy.
2. Briefly define the following characteristics of hard drives: (a) seek time, (b) rotational latency, (c) transfer time.
3. Suppose the odds that a disk drive fails in a given year is 1/7. Suppose we are using Raid 4 with three drives. What is the mean time till data is lost if it takes 5 hours to replace a broken drive?
4. What is pointer swizzling? Briefly explain and give a concrete example of a block before and after pointer swizzling and an example situation where a swizzled pointer might be followed.
5. Explain with steps and an example how record insertion within a block is handled in the sorted records case.
6. Define the following terms: (a) Sequential file, (b) dense index, (c) clustered index.
7. What is the ISAM record format? Briefly describe the column schema of the sqlite_master table.
8. Give an example of a kd-tree with more than 4 leaves that queries at least two distinct attributes and which queries at least one of these twice. Explain how a look up could be performed on this tree.
9. Explain and give an example of how two pass sorting can be used to do grouping and aggregation.
10. Suppose the block size was 4096, where 91 bytes are used for header info. Suppose had a 4,000,000 tuple relation. Suppose tuple size goes from 60 bytes long to 10 bytes long after a projection. How many block would be needed to store all the tuple before and after doing this projection?