DBMS

21. What is called block-level striping? 

Block level striping stripes blocks across multiple disks. It treats the array of disks  as a large disk, and gives blocks logical numbers. 

22. What are the two main goals of parallelism? 

. Load –balance multiple small accesses, so that the throughput of such  accesses increases. 

. Parallelize large accesses so that the response time of large accesses is reduced 

23. What are the factors to be taken into account when choosing a RAID level? 

o Monetary cost of extra disk storage requirements. 

o Performance requirements in terms of number of I/O operations 

o Performance when a disk has failed. 

o Performances during rebuild. 

24. What is meant by software and hardware RAID systems? 

RAID can be implemented with no change at the hardware level, using only software modification. Such RAID implementations are called software RAID systems and the systems with special hardware support are called hardware RAID systems. 

25. Define hot swapping? 

Hot swapping permits the removal of faulty disks and replaces it by new ones 

without turning power off. Hot swapping reduces the mean time to repair. 



 26. Which level of RAID is best? Why? 

RAID level 1 is the RAID level of choice for many applications with moderate 

storage requirements and high I/O requirements. RAID 1 follows mirroring and provides 

best write performance. 

27. Distinguish between fixed length records and variable length records? 

Fixed length records 

Every record has the same fields and field lengths are fixed. 

Variable length records 

File records are of same type but one or more of the fields are of varying size. 

28. What are the ways in which the variable-length records arise in database systems? 

• . Storage of multiple record types in a file. 
• . Record types that allow variable lengths for one or more fields. 
• . Record types that allow repeating fields. 

29. Explain the use of variable length records. 

• . They are used for Storing of multiple record types in a file. 
• . Used for storing records that has varying lengths for one or more fields. 
• . Used for storing records that allow repeating fields 

30. What is the use of a slotted-page structure and what is the information present in the header? 

• The slotted-page structure is used for organizing records within a single block. 
• The header contains the following information. . 
• The number of record entries in the header. 
• The end of free space 
• An array whose entries contain the location and size of each record.