CHAPTER 7 Dbms

Question 1

DATA RECOVERY

Answer 1

THE DEFINATION OF DATABASE RECOVERY IS THE PROCESS OF RESTORING THE DATA BASE TO THE MOST RECENT CONSISTENT STATE THAT EXISTED JUST BEFORE THE FALIURE

Question 2

LOG RECOVERY

Answer 2

LOG IS A SEQUENCE OF RECORDS , WHICH MAINTAINS THE RECORDS OF ACTIONS PERFORMED BY A TRANCATION . - THE LOG FILE IS KEPT ON STABLE STORAGE MEDIA.
- WHEN TRANSACTION ENTERS THE SYSTEM AND STARTS EXECUTION, IT WRITES A LOG ABOUT IT
- in log base recovery all results are depend on logs after failure

Question 3

TYPES OF DATABASE RECOVERY (LOG BASE )

Answer 3

DEFERRED DATABASE MODIFICATION
IMMEDIATE DATABASE MODIFICATION

Question 4

DEFERRED DATABASE MODIFICATION

Answer 4

THE DATABASE IS UPDATED WHEN TRANCATION IS COMMITED
IF TRANSCATION COMMITS, IT APPLIED REDO AND OLD DATABASE VALUE REPLACED BY NEW
in deferred we only store new value not old value