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.

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