Question

7. a) Which mechanism guarantees exclusive use of the database record?........... b) What does de-duplication prevent? 8. a) How many tapes do we need in the 3-level small business database backup? .. b) What does 0-level backup tape contain? 9. a) What sort of point in time backups are snapshots? b) Are snapshots operating on the file or block level?.... 10. a) What does MySQL shell command SELECT min(sal), Max (sal), av g(sal) FROM tablex; return? b) Are the same functions available in R console shell?.....................

Answer 1

Note: Multiple questions posted, all the subparts of first two questions are solved below. a): Locking Explanation: The locking is the mechanism used by DBMS systems to exclusively access a data base record. The locking will make the record inaccessible for other applications or users, thus only the application that make the lock on the record can use that record. Thus the record can be exclusively used by locking mechanism. b): Duplicate copies of repeating data Explanation: The de- duplication of the data bases will eliminate the duplicate entries of the database. The de- duplication not simply removing the duplicate entries only the redundant data will be removed, not the data that defined for establishing dependency will not. Thus the de - duplication for establishing dependency will not. Thus the de - duplication will remove the duplicate copies of repeating data. a): Four Explanation: The level - 3 database