GATE CSE 2017 SET-1
Q51.
In a database system, unique time stamps are assigned to each transaction using Lamport's logical clock . Let TS(T_{1}) and TS(T_{2}) be the timestamps of transactions T_{1} and T_{2} respectively. Besides, T_{1} holds a lock on the resource R, and T_{2} has requested a conflicting lock on the same resource R. The following algorithm is used to prevent deadlocks in the database system assuming that a killed transaction is restarted with the same timestamp. Assume any transactions that is not killed terminates eventually. Which of the following is TRUE about the database system that uses the above algorithm to prevent deadlocks?Q53.
Consider a TCP client and a TCP server running on two different machines. After completing data transfer, the TCP client calls close to terminate the connectional and a FIN segment is sent to the TCP server. Server-side TCP responds by sending an ACK which is received by the client-side TCP. As per the TCP connections state diagram (RFC 793), in which state does the client-side TCP connection wait for the FIN from the sever-side TCP?Q54.
Let A and B be infinite alphabets and let # be a symbol outside both A and B. Let f be a total functional from A* to B*. We say f is computable if there exists a Turning machine M which given an input x in A*, always halts with f(x) on its tape. Let L_{f} denote the language {x#f(x)|x\inA*}. Which of the following statements is true:Q55.
Consider a combination of T and D flip-flops connected as shown below. The output of the D flip-flop is connected to the input of the T flip-flop and the output of the T flip-flop is connected to the input of the D flip-flop Initailly, both Q_{0} and Q_{1} are set to 1 (before the 1st clock cycle). The outputsQ56.
Consider a database that has the relation schemas EMP(EmpId, EmpName, DepId) and DEPT(DeptName, DeptId). Note that the DeptId can be permitted to be NULL in the relation EMP. Consider the following queries on the database expressed in tuple relational calculus. Which of the above queries are safe?