Q. An actual update is not allowed to a data item :

View solution

Q. The undo and redo operations must be _________ to guarantee correct behaviour, even if a failure occurs during recovery process.

View solution

Q. The system periodically performs checkpoints that consists of the following operation(s) :

View solution

Q. Consider a transaction T1 that committed prior to checkpoint. The <T1 commits> record appears in the log before the <checkpoint> record. Any modifications made by T1 must have been written to the stable storage either with the checkpoint or prior to it. Thus at recovery time:

View solution

Q. Serializable schedules are ones where :

View solution

Q. A locking protocol is one that :

View solution

Q. The two phase locking protocol consists of :

View solution

Q. The growing phase is a phase in which :

View solution

Q. The shrinking phase is a phase in which :

View solution

Q. The following program consists of 3 concurrent processes and 3 binary semaphores. The semaphores are initialized as S0 = 1, S1 = 0, S2 = 0.

Process P0
while(true)
{
wait(S0);
print '0';
release(S1);
release(S2);
}

Process P1
wait(S1);
release(S0);

Process P2
wait(S2);
release(S0);

How many times will P0 print ‘0’ ?

View solution

Q. Each process Pi, i = 0,1,2,3,……,9 is coded as follows :

repeat
P(mutex)
{Critical Section}
V(mutex)
forever

The code for P10 is identical except that it uses V(mutex) instead of P(mutex). What is the largest number of processes that can be inside the critical section at any moment (the mutex being initialized to 1)?

View solution

Q. Two processes, P1 and P2, need to access a critical section of code. Consider the following synchronization construct used by the processes :

Process P1 :
while(true)
{
w1 = true;
while(w2 == true);
Critical section
w1 = false;
}
Remainder Section

Process P2 :
while(true)
{
w2 = true;
while(w1 == true);
Critical section
w2 = false;
}

Here, w1 and w2 are shared variables, which are initialized to false. Which one of the following statements is TRUE about the above construct?

View solution

Q. The following pair of processes share a common variable X :

Process A
int Y;
A1: Y = X*2;
A2: X = Y;

Process B
int Z;
B1: Z = X+1;
B2: X = Z;


X is set to 5 before either process begins execution. As usual, statements within a process are executed sequentially, but statements in process A may execute in any order with respect to statements in process B.
How many different values of X are possible after both processes finish executing ?

View solution

Q. The program follows to use a shared binary semaphore T :

Process A
int Y;
A1: Y = X*2;
A2: X = Y;
signal(T);

Process B
int Z;
B1: wait(T);
B2: Z = X+1;
X = Z;


T is set to 0 before either process begins execution and, as before, X is set to 5.
Now, how many different values of X are possible after both processes finish executing ?

View solution

Q. All processes share a semaphore variable mutex, initialized to 1. Each process must execute wait(mutex) before entering the critical section and signal(mutex) afterward.
Suppose a process executes in the following manner :

signal(mutex);
.....
critical section
.....
wait(mutex);

In this situation :

View solution

Q. All processes share a semaphore variable mutex, initialized to 1. Each process must execute wait(mutex) before entering the critical section and signal(mutex) afterward.
Suppose a process executes in the following manner :

wait(mutex);
.....
critical section
.....
wait(mutex);

In this situation :

View solution

Q. Consider the methods used by processes P1 and P2 for accessing their critical sections whenever needed, as given below. The initial values of shared boolean variables S1 and S2 are randomly assigned.

Method used by P1 :
while(S1==S2);
Critical section
S1 = S2;

Method used by P2 :
while(S1!=S2);
Critical section
S2 = not(S1);

Which of the following statements describes properties achieved ?

View solution

Q. Which of the following concurrency control protocols ensure both conflict serializability and freedom from deadlock ?

I) 2-phase locking
II) Time-stamp ordering

View solution

Q. The initial value of the semaphore that allows only one of the many processes to enter their critical sections, is

View solution

Q. For how many processes which are sharing common data, the Dekker's algorithm implements mutual exclusion?

View solution