Basic CS [3i Infotech Placement]: Sample Questions 72 - 73 of 243

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Question 72


Describe in Detail


What is Process migration?


Process, Virtual Machine, and OS Migration
  • Migration is a form of process management- process is moved from one computing environment to another.
  • Involves transfer of sufficient state of process from one machine to the target machine.
  • Enables dynamic load distribution, fault resilience, eased system administration, and data access locality.

Two Types of Process Migration

  • Non-pre-emptive process migration:
    • Takes place before execution of the process starts.
    • Relatively cheap.
  • Pre-emptive process migration:
    • Process is pre-empted, migrated and continues processing in a different execution environment.
    • Relatively expensive- involves recording, migration and recreation of the process state.

Steps Involved in Process Migration

  • Freezing the process on source.
  • Transferring the process address space from source to destination.
  • Restarting the process on destination
  • OS forward messages to the new destination for the migrant process- handling communication between cooperating processes.

Question 73


Write in Short

Short Answer▾

What are the rings in Windows NT?


Ring Window NT in Image
  • Rings provides the separation between the user mode and kernel mode for different processes.
    • Kernel mode: (ring 0)
      • Executive run in protected memory mode with full privileges.
    • User mode: (ring 3)
      • Runs with privileges to access its own memory area.
      • User applications and environment subsystems execute in mode.

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