Questions tagged [database-concurrency]

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Proof that 2 phase locking produces order preserving Conflict serializable schedules

In the book Transactional information systems: theory, algorithms, and the practice of concurrency control and recovery there is a theorem stating that Gen(2PL) ⊂ OCSR. Can some one help to guide on ...
Abishek0398's user avatar
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1 answer

How are blind writes recoverable in a transaction schedule?

Consider the following schedule - T1 T2 R(A) W(A) R(A) W(A) Commit Commit I understand that this schedule is non-recoverable, because if ...
Kushagr Jaiswal's user avatar
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Checking if Schedule is recoverable

Consider the following schedule S.Is S conflict–serializable? Append the commit operations of these transactions at the end of the schedule in an appropriate order such that S is recoverable. How many ...
bigstreet's user avatar
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What will you do if multiple users access your application at the same time?

I'm an experienced Software Engineer but very weak in concurrency because of no prior experience in that. I've been interviewing with several companies in which I was asked similar kinds of questions ...
KhiladiBhaiyya's user avatar
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2 answers

how two phase commit ensure serializability

Two phase commit is used in distributed transaction. For example, a client sends a transaction to two databases with a coordinator. step1: client get a global transaction id from coordinator step2: ...
gaoxinge's user avatar
  • 101
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Does basic 2 PL always ensure conflict serializability?

While going through the DBMS book by Korth, it was mentioned : " For a set of transactions, there may be conflict-serializable schedules that cannot be obtained through the two-phase locking ...
mahesh 2222's user avatar
2 votes
1 answer

Why do OS and DBMS have their own synchronisation mechanisms, when OS can alone do it and it sits at the bottom of DB?

I know that synchronization is important in the OS, but why do we need a separate topic synchronization and concurrency in the DBMS? The OS concentrates on program synchronization while the DBMS ...
mahesh 2222's user avatar