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Fundamentals Of Database Systems: Pearson

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Question:

Describe about the Fundamentals of Database Systems for Pearso?
 
 

Answer:

Ch 21: Introduction to Transaction Processing Concepts and Theory

Figure 21.2 is,

Now the transaction T2 is changes into,

T2

read_item(X);

X:= X+M;

if X > 90 then exit

else write_item(X);

Based on the changed transaction details, the schedules,

Will run and outcome from schedule (a) will be, X is only 2 less than the initial value and Y is 2 more than the initial value. But, the problem of lost update will exist. Adding the condition will have no effect on the previous problem.

For schedule (b) if the initial value of X is 92 or more then X will be updated by T1 only, the update by T2 will have no effect.

The number of serial schedule possible are 6. Those are,

T1à T2 à T3

T1àT3àT2

T3àT2àT1

T2àT1àT3

T2àT3àT1

T3àT1àT2

Total number of possible schedule is 3! = 6.

A transaction should work as an atomic transaction. So there will be only one point of beginning of a transaction. Hence, an explicit begin is not necessary as this is trivial. On the other hand, there may be two different cases, of ending a transaction on a database. The ending can be either by committing the transaction successfully or due to some abort operation. So, an explicit end command is needed to ensure valid and successful ending of a transaction on a database.

Ch 22: Concurrency Control Techniques

In case of strict two phase locking protocol, if there is two transactions, then one have to wait for another to commit. Once one transaction is committed, then other can read the data. So, this condition ensures strict serializability of transactions under two phase locking protocol. Hence, proved.

 

Ch 23: Database Recovery Techniques

No, no differences will be made in the recovery process. The read_item operations are needed only to determine the cascading rollbacks if there is any additional transaction.

The transactions T1 and T2 both are not committed yet, when the system crashes. Thus those transactions will be rolled back in the recovery process.

There are some difference with ARIES. In ARIES, the modified memory buffers are not flushed into the disks. The additional information are written on the log file as a transaction table. A additionally a dirty page table is written during check pointing.

In a ‘No Steal’ case, no updates on some buffered page will be written back to the disks before commitment of the transaction. On the other hand, ‘force’ means, updates on such pages will be written at the time of commitment of a transaction.

In case of check pointing, ‘No steal’ refers to the scheme that the modification of the main memory buffers will not be written back to the disk when some uncommitted transactions are updating the pages on main memory. In case of ‘force’, when a transaction is over, the updates will be written back to the disk. Failure in doing so, will need a ‘Redo’ command. It does not need any ‘Undo’ command as there is no uncommitted updates propagation to the disks.

Ch 24: Database Security

The limit on horizontak propagation will be 5 and limit on vertical propagation will be up to level 1 for USER_A. So, USER_A can grant using GRANT command to at most 5 other users. Then no more granting is possible by USER_A.

NAME

SALARY

JobPerformance

TC

Smith     U

Null      U

Null            U

U

 

When a classification U user tries to update SALARY or Smith to $50000 then the 3rd poly instantiation of the Smith tuple will happen. The result will be

NAME

SALARY

JobPerformance

TC

Smith     U

40000      C

Fair            S

S

Smith      U

40000      C

Excellent     C

C

Smith      U

50000      U

Null       U

U

Brown         C

80000      S

Good     C

S

 

References:

Elmasri, R., & Navathe, S. B. (2013). Fundamentals of Database Systems. Pearson .

Mullins, C. S. (2013). Database Administration: The Complete Guide to DBA Practices and Procedures. Addison-Wesley Professional.

Özsu, M. T., & Valduriez, P. (2011). Principles of Distributed Database Systems. Springer.

Rahimi, S. K., & Haug, F. S. (2010). Distributed Database Management Systems. John Wiley & Sons.

Silberschatz, A., Korth, H. F., & Sudarshan, S. (2011). Database System Concepts (6th ed.). McGraw-Hill.

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