UNIVERSITY OF HOUSTON
                 Department of Computer Science
                                
                  COSC 6360--Operating Systems
              QUALIFYING EXAMINATION-Graduate Part
                    FINAL EXAMINATION-Part II
                          May 13, 1999
                                
This exam is closed book.  You can have two sheets (i.e., four
pages) of notes.

1.  File Systems:
    In opposite to what happened ten years ago, disk drive
    capacities are now increasing at a faster rate than main
    memory capacities.  How should this evolution affect log-
    structured file systems (LFS)?  What changes would you bring
    to improve their performance?  (20 points)

2.  Extending Remote Procedure Calls:
    How would you extend the remote procedure call model to let
    them handle C++ or Java style objects?  The CORBA solution
    is quite interesting: while elementary data types such as
    integers, floating-point numbers and so forth continue to be
    passed by value, more complex objects are passed by reference,
    which forces the server to call back the client every time it
    wants to access any object.

    What are the advantages and disadvantages of this solution?
    Can you think of other possible approaches?  What would be
    their advantages and disadvantages?  (20 points)
     

                     UNIVERSITY OF HOUSTON
                 Department of Computer Science
                                
                  COSC 6360--Operating Systems
                    FINAL  EXAMINATION-Part I
                          May 13, 1999
                                
This exam is closed book.  You can have two sheets (i.e., four
     pages) of notes.

1.   Give your own example of an anomalous behavior in a
     distributed system using logical clocks.  (5 points)  Under
     which condition could this anomalous behavior still happen 
     in a system using physical clocks. (5 points)
   
2.   What needs to be done if the private key of the Kerberos
     ticket granting service (TGS) becomes known to one or more
     intruders? (10 points)

3.   What makes the Bullet file system so fast? (5 points)  What are
     the limitations of the approach (5 points)

4.   What is the major motivation for AFS callbacks? (5 points)
     What is their major disadvantage and how does AFS solve that
     problem? ( 5 points)

5.   What is a witness and what is their major advantage? (5 points)

6.   Why does Grapevine assign by default several mailboxes to
     each individual user?  (5 points)

7.   Why did the designers of Sprite decide to use ordinary
     Sprite files as backing storage for their virtual memory
     system? (10 points)