Database Systems 6th Edition by Ramez Elmasri, Shamkant B. Navathe

تمرين 12

Suppose that a disk unit has the following parameters: seek time s=20 msec; rotational delay rd=10 msec; block transfer time btt=1 msec; block size B=2400 bytes; interblock gap size G=600 bytes. An EMPLOYEE file has the following fields: SSN, 9 bytes; LASTNAME, 20 bytes; FIRSTNAME, 20 bytes; MIDDLE INIT, 1 byte; BIRTHDATE, 10 bytes; ADDRESS, 35 bytes); PHONE, 12 bytes); SUPERVISORSSN, 9 bytes; DEPARTMENT, 4 bytes; JOBCODE, 4 bytes; deletion marker, 1 byte. The EMPLOYEE file has r=30000 STUDENT records, fixed-length format, and unspanned blocking. Write down appropriate formulas and calculate the following values for the above EMPLOYEE file:
(a) The record size R (including the deletion marker), the blocking factor bfr, and the number of disk blocks b.
(b) Calculate the wasted space in each disk block because of the unspanned organization.
(c) Calculate the transfer rate tr and the bulk transfer rate btr for this disk (see Appendix B for definitions of tr and btr).
(d) Calculate the average number of block accesses needed to search for an arbitrary record in the file, using linear search.
(e) Calculate the average time needed in msec to search for an arbitrary record in the file, using linear search, if the file blocks are stored on consecutive disk blocks and double buffering is used.
(f) Calculate the average time needed in msec to search for an arbitrary record in the file, using linear search, if the file blocks are not stored on consecutive disk blocks.
(g) Assume that the records are ordered via some key field. Calculate the average number of block accesses and the average time needed to search for an arbitrary record in the file, using binary search.