Ch 37: Hashing Techniques in Databases

While recovering database data after a sudden system crash or failure, which of the following files does the DBMS recovery manager examine first to identify transaction states?

-- Crash Recovery Scan Order:
-- Checkpoint -> Read Log Sequentially -> UNDO Active -> REDO Committed

In database crash recovery, the recovery manager maintains several files to reconstruct the database state after a sudden failure. Match the following recovery structures with their correct definitions: 1. Log File - A. A sequential file recording all database updates, transaction starts, commits, and rollbacks. 2. Checkpoint - B. A periodic reference point in the log file showing that all modified cache buffers are written to the disk. 3. Active Transactions - C. A list of transactions that were currently running and uncommitted when the system crashed.

-- Log Record entry:
-- <T1, Var_X, Old_Value, New_Value>

While recovering database data after a sudden system failure or physical crash, which of the following files does the DBMS recovery manager examine first?

-- Recovery Manager sequence:
-- Checkpoint -> Scan Log Sequentially -> UNDO Active -> REDO Committed

During a database crash recovery process, which of the following files does the DBMS recovery manager examine first to identify uncommitted transactions that must be undone and committed transactions that must be redone?

-- Sequential recovery log scanning:
-- Checkpoint -> Scan Log -> Undo Active -> Redo Committed

Under physical database index structures, which of the following statements is NOT true regarding indexes?

-- Creating a composite index on multiple attributes:
CREATE INDEX idx_emp_dept ON EMPLOYEE (DeptID, Salary);

Which of the following statement is strictly true regarding the creation and existence of search indexes in a relational database?

CREATE INDEX idx_student_gpa ON STUDENT (cgpa DESC);