Questions tagged [database-concurrency]

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Does timestamp protocol following thomas's write rule allow non-view-serializable schedules in some cases?

I have came across following line in text book (Database System Concepts Textbook by Avi Silberschatz, Henry F. Korth, and S. Sudarshan $6e$) page no. 686: Thomas’ write rule allows schedules that ...
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Does graph based protocol in DBMS suffer from starvation issues?

I know that graph based protocols require prior knowledge of access of data items. Besides when a transaction locks some data item in graph based protocol it also locks some unnecessary data items ...
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20 views

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 ...
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217 views

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 ...
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Understanding non repeatable read anomaly in databases

This paper discusses in detail ANSI isolation levels discussed in ANSI SQL standard on page 84. Paper introduces following shorthand for describing histories which contain reads, writes, commits and ...
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Understanding repeatable read isolation level

Wikipedia defines following terms: With a lock-based concurrency control DBMS implementation, serializability isolation level requires read and write locks (acquired on selected data) to be ...