51 votes 51 votes Which of the following concurrency control protocols ensure both conflict serializability and freedom from deadlock? $2$-phase locking Time-stamp ordering I only II only Both I and II Neither I nor II Databases gatecse-2010 databases transaction-and-concurrency normal + – go_editor asked Sep 29, 2014 • edited Jun 17, 2021 by Lakshman Bhaiya go_editor 22.8k views answer comment Share Follow See all 3 Comments See all 3 3 Comments reply jaswanth431 commented Sep 9, 2021 i edited by jaswanth431 Sep 9, 2021 reply Follow Share Protocol Serializable Schedules? Deadlock possible? Starvation possible? Generated Schedules Basic 2PL Yes Yes Yes May not be recoverable Strict 2PL Yes Yes Yes Strict schedules Rigorous 2PL Yes Yes Yes Strict schedules Conservative 2PL Yes No Yes May not be recoverable Graph based protcol Yes No May not be recoverable Time stamp ordering Yes No Yes May not be recoverable Thomas write rule Yes No Yes Same as Time stamp ordering and some view serializable schedules are generated. http://cs.iit.edu/~cs425/slides/ch10-cc.pdf please let me know if any thing is wrong 14 votes 14 votes ankit3009 commented Dec 20, 2021 reply Follow Share @adad20 Please verify whether the above table seems correct to you or not. It seems correct to me. 1 votes 1 votes Chhaatra commented Dec 20, 2021 reply Follow Share Some values seems to be ambiguous to me :( @jaswanth431 Bro are you sure it's correct ? 0 votes 0 votes Please log in or register to add a comment.
2 votes 2 votes 2 Phase Locking (2PL) is a concurrency control method that guarantees serializability. The protocol utilizes locks, applied by a transaction to data, which may block (interpreted as signals to stop) other transactions from accessing the same data during the transaction’s life. 2PL may be lead to deadlocks that result from the mutual blocking of two or more transactions. See the following situation, neither T3 nor T4 can make progress. Timestamp-based concurrency control algorithm is a non-lock concurrency control method. In Timestamp based method, deadlock cannot occur as no transaction ever waits. Paras Nath answered Apr 16, 2018 Paras Nath comment Share Follow See all 0 reply Please log in or register to add a comment.
0 votes 0 votes Consider about the case of Strict 2PHASE locking protocol, it is not deadlock free Also Time stamp ordering is no guarantee to have conflict serialisabilty HENCE D is answer shashankrustagi answered Jan 20, 2021 shashankrustagi comment Share Follow See 1 comment See all 1 1 comment reply viral8702 commented Oct 21, 2023 reply Follow Share Wrong Answer. don’t just write answer for getting points. 0 votes 0 votes Please log in or register to add a comment.