CS542 Distributed Database Systems
Prof. Bharat Bhargava

Assignment 2

Each question carries 10 points. This assignment is due on February 11, 2016.

Q1: Comment on the suitability of using variations of:  (a) locking, (b) time stamps, and (c) versions  for concurrency control. You may use examples.

Q2: What are the different ideas for increasing the degree of concurrency? You may give examples.

Q3: Read the following paper: A Model for Adaptable Systems for Transaction Processing, Bharat Bhargava and John Riedl, IEEE Transactions on Knowledge and Data Engineering, 1(4), Dec 1989.
a) What do we mean by adaptability in transaction processing?
b) Can you switch between timestamp and locking based algorithms? What transformations are needed?
You may give examples.

Q4: Assume that we use centralized control and issue updates to all sites after the transaction has been committed at the central site.
a) How can we ensure mutual consistency?
b) What ideas can be used to reduce waiting at other sites?

Questions from Assignment 1 (if you didn't complete them):

Q5: Try to read the paper: The serializability of concurrent database updates, C. Papadimitriou, Journal of the ACM (JACM), 26(4), 1979
What are the different performance criteria for evaluating concurrency control algorithms?
What is the difference between class DSR and 2PL?
When DSR is equivalent to SR class of concurrency control?

Q6: Read the paper Granularity of Locks and Degrees of Consistency in a Shared Data Base by J. Gray, R. Lorie, G. Putzolu, I. Traiger.
What are advantages and disadvantages of multiple-granularity locks? (10 points)