Distributed Database Question Bank with Answers 17

Distributed  and parallel database questions and answers for University exams

Question:

What is the major disadvantage of 2PC protocol? [Discuss the Blocking problem of 2PC]

Answer:

The major disadvantage of two phase commit protocol is Blocking problem.

Blocking problem – This happens is the transaction coordinator fails. In case of coordinator failure, 2PC uses various ways to complete the transaction (to abort or commit). It can be done using the messages found in the log files of participating sites. If all the participating sites have <ready T> message and no other control messages (such as <abort T> or <commit T>) then all the active sites which are participating in that transaction have to wait for their transaction coordinator to recover. This indefinite blocking with locks held is called blocking problem.

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