UNIVERSITY OF HOUSTON
              Department of Computer Science
               COSC 6360: Operating Systems
                    FINAL EXAMINATION
                Part I:  General Questions
                  QUALIFYING EXAMINATION 
                 Part A:  Graduate Topics
                       May 7,  1992

CLOSED BOOK: You may have with you two sheets of notes.

1.  In their latest paper on Amoeba, Tanenbaum et al. state that:

    The scheduling of threads within a process is done by code within
    the process itself.  When a thread blocks, either because it has no
    work to do (i.e., on a GET_REQUEST) or because it is waiting for a
    remote reply (i.e., on a DO_OPERATION), the internal scheduler is
    called, the thread is blocked and a new thread can be run.

    Contrast their approach with other implementations of threads and
    highlight its benefits. (20 points)

2.  With today's large address spaces, it becomes feasible to MAP
    entire files in the virtual address spaces of the processes
    accessing the file.  Consider a mapped file system with the
    following two operations:

    ptr = map (filename, access),

    which maps the file into the virtual address space of the calling
    process and returns the starting address of the mapped file, and

    unmap(<filename>),

    which undoes the mapping.

    Note the absence of read() and write() primitives.

    Describe in some detail a possible implementation of a distributed
    MAPPED file system providing UNIX sharing semantics. (20 points)



		  UNIVERSITY OF HOUSTON
              Department of Computer Science
               COSC 6360: Operating Systems
                    FINAL EXAMINATION
               Part II:  Specific Questions
                      May 7,  1992

CLOSED BOOK: You may have with you two sheets of notes.

1.  What are the two new system mechanisms that have been added to the
    Ninth Edition Unix System?  (10 points) Explain in a few lines how
    these mechanisms can be used to establish a network connection
    between two processes. (5 points)

    THIS QUESTION WAS RELATED TO A PAPER THAT IS NOT ANYMORE IN THE
    READING LIST.  IT WILL BE NOT BE ASKED AGAIN.

2.  State in two or three lines the most important limitation of
    STATELESS file servers. (5 points)

3.  Describe in some detail the sharing semantics of Andrew. (10 points)

4.  What is a VERSION VECTOR? (5 points)  How can version vectors be
    used to detect inconsistencies between replicas of the same file?
    (5 points)

5.  According to Liskov et al., what is the major benefit of adding 
    uninterruptible power supplies to all HARP servers? (10 points)

6.  How does the Bullet file server store files on disk? Why? (5
    points)

7.  Explain in a few lines what Nelson et al. mean by "Sequential
    Write Sharing." (5 points)