MC	Which statement is NOT CORRECT?	Archiving is an approach in which database files are copied periodically to other storage media, such as tape or (another) hard disk. 	incorrect	Disk mirroring is a (near) real time approach that writes the same data simultaneously to two or more physical disks	incorrect	There is a trade-off between the cost (overhead and storage cost) of more frequent backups and the cost of lost data because of less frequent backups.	incorrect	Traditional relational databases allow for a certain measure of temporary inconsistency, in return for increased performance.	correct	
MC	The following figure presents five transactions (T1 until T5) that are executed more or less simultaneously. Suppose a checkpoint was registered on the logfile at time tc, marking the last time when pending updates in the database buffer were persisted into the physical database files. Later, at time tf, a system fault occurred, resulting in loss of the database buffer.<br><img class="img-fluid" src="http://www.pdbmbook.com/static/quiz/fig14_5.png"><br>What recovery operations are required?	T1: nothing; T2: REDO; T3: UNDO; T4: REDO; T5: nothing	correct	T1: nothing; T2: REDO; T3: REDO; T4: REDO; T5: nothing	incorrect	T1: REDO; T2: UNDO; T3: REDO; T4: nothing; T5: nothing	incorrect	T1: nothing; T2: UNDO; T3: REDO; T4: REDO; T5: nothing	incorrect	
MC	Which statement is NOT CORRECT?	Disk mirroring is a (near) real time approach that writes the same data simultaneously to two or more physical disks	incorrect	There is a trade-off between the cost (overhead and storage cost) of more frequent backups and the cost of lost data because of less frequent backups.	incorrect	Traditional relational databases allow for a certain measure of temporary inconsistency, in return for increased performance.	correct	Archiving is an approach in which database files are copied periodically to other storage media, such as tape or (another) hard disk. 	incorrect	
MC	The following figure presents five transactions (T1 until T5) that are executed more or less simultaneously. Suppose a checkpoint was registered on the logfile at time tc, marking the last time when pending updates in the database buffer were persisted into the physical database files. Later, at time tf, a system fault occurred, resulting in loss of the database buffer.<br><img class="img-fluid" src="http://www.pdbmbook.com/static/quiz/fig14_5.png"><br>What recovery operations are required?	T1: nothing; T2: REDO; T3: UNDO; T4: REDO; T5: nothing	correct	T1: REDO; T2: UNDO; T3: REDO; T4: nothing; T5: nothing	incorrect	T1: nothing; T2: REDO; T3: REDO; T4: REDO; T5: nothing	incorrect	T1: nothing; T2: UNDO; T3: REDO; T4: REDO; T5: nothing	incorrect	
MC	Which statement is NOT CORRECT?	The logfile contains all updates after they have been written to disk. 	correct	The logfile can be implemented as a sequential file.	incorrect	The logfile contains redundant data.	incorrect	The logfile is often duplicated, e.g. in a RAID level 1 configuration.	incorrect	
MC	If the precedence graph contains a cycle, the schedule is...	serializable	incorrect	not serializable	correct	
MC	If the precedence graph contains a cycle, the schedule is...	not serializable	correct	serializable	incorrect	
MC	When a transaction is aborted, it is important that:	A rollback of the transaction is executed: all changes made by the transaction's respective operations should be undone.	correct	All changes made by the individual operations belonging to that transaction should be made permanent.	incorrect	
MC	If the precedence graph contains a cycle, the schedule is...	not serializable	correct	serializable	incorrect	
MC	Which statement is CORRECT?	Multiple transactions may hold a shared lock on the same object.	correct	Multiple transactions may hold an exclusive lock on the same object.	incorrect