TRENDS IN DATABASE TECHNOLOGY

1. What are the advantages and disadvantages of indexed sequential file? APRIL/MAY-

2011

The advantage of ordering records in a sequential file according to a key is that you can then

search the file more quickly. If you know the key value that you want, you can use one of the relatively fast searches. The disadvantage is that when you insert, you need to rewrite at least everything after the insertion point, which makes inserts very expensive unless they are done at the end of the file. An indexed file approach keeps a (hopefully) small part of each row, and some kind of "pointer" to the row's location within the data file. This allows a search to use the index, which is ordered by the index and (again hopefully) much smaller and therefore much faster than scanning the entire data file for the indexed data.

2. What is database tuning? APRIL/MAY-2011

Database tuning describes a group of activities used to optimize and homogenize the

performance of a database. It usually overlaps with query tuning, but refers to design of the database files, selection of the database management system (DBMS), operating system and CPU the DBMS runs on.

3. Give the measures of quality of a disk.

Capacity

Access time

Seek time

Data transfer rate

Reliability

Rotational latency time.

Cheaper than disk Expensive when compared with disk

5. What are the types of storage devices?

Ø Primary storage

Ø Secondary storage

Ø Tertiary storage

6. Define average seek time.

The average seek time is the average of the seek times, measured over a sequence of random

requests.

7. Define rotational latency time.

The time spent waiting for the sector to be accessed to appear under the head is called the

rotational latency time.

8. Define average latency time.

The average latency time of the disk is one-half the time for a full rotation of the disk.

9. What is meant by data-transfer rate?

The data-transfer rate is the rate at which data can be retrieved from or stored to the disk.

10. What is meant by mean time to failure?

The mean time to failure is the amount of time that the system could run continuously without

failure.