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Thrashing is said to occur when the system spends a large amount of time transferring shared data blocks from one node to another, compared to the time spent doing the useful work of executing application  processes. It is serious performance problem with DSM systems that allow data blocks to migrate from one node to another. Thrashing may occur in the following situations: a.  When interleaved data accesses made by processes on two or more nodes causes a data block to move back and forth from one node to another in quick succession. b.  When blocks with read-only permissions are invalidated soon after they are replicated. Following methods may be used to solve the thrashing problem in DSM systems: a.  Providing  application-controlled  locks.  Locking  data  to  prevent  other  nodes  from accessing that data for a short period of time can reduce thrashing. b.  Nailing a block to a node for a minimum amount of time. Another method to reduce thrashing is to disallow a block to be take

Interview questions based on important concepts in computer network. Question 1 Can you guess why IPv6 (Internet Protocol version 6) addresses came into existence while still IPv4 is being used by many machines? Answer : The only reason could be the enormous growth in the number of machines using v4 addresses. This forces concerned agencies to raise the address pool by some means. One of such ways was the introduction of IPv6 so that more machines can be accommodated. Question 2 Consider two network layer devices, one operating at network layer and the other operating at data link layer. In very generic terms, which one is more intelligent ? Explain with example. Answer : Generally a device that operates at a higher layer in OSI model is intelligent. For example, there are switches that operate at data link layer and some others that operate at network layer. Simply due to the additional capabilities of the switches that operate in network layer they can be