DBMS

11. What are a block and a block number?

A block is a contiguous sequence of sectors from a single track of one platter. Each request

specifies the address on

the disk to be referenced. That address is in the form of a block number.

12. What are called journaling file systems?

File systems that support log disks are called journaling file systems.

13. What is the use of RAID?

A variety of disk-organization techniques, collectively called redundant arrays of independent

disks are used to improve the performance and reliability.

14. Explain how reliability can be improved through redundancy?

The simplest approach to introducing redundancy is to duplicate every disk. This technique is called mirroring or shadowing. A logical disk then consists of two physical disks, and write is

carried out on both the disk. If one of the disks fails the data can be read from the other. Data will be lost if the second disk fails before the first fail ed disk is repaired.

15. What is called mirroring?

The simplest approach to introducing redundancy is to duplicate every disk. This technique is called mirroring or shadowing.

16. What is meant by Multi-dimensional database?

A multi-dimensional database is a computer software system designed to allow for efficient and

convenient storage and retrieval of large volumes of data that is (1) intimately related and (2) stored, viewed and analyzed from different perspectives and these perspectives are called dimensions.

17. What is meant by Spatial database?

A spatial database is a database that is optimized to store query data that represents objects

defined in geometric space. Most spatial databases allow representing simple geometric objects such as points, lines and polygons. Some spatial databases handle more complex structures such as 3D objects, topological coverages,etc.

18. What is meant by Mobile database?

A mobile database is a database that resides on mobile device such as a PDA, a smart phone, or a

laptop. Such devices are often limited in resources such as memory, computing power and battery power.

top-alt:auto;mso-margin-bottom-alt:auto; line-height:normal'>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.