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What Is Concurrency In Dbms?

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Users submit transactions, and can think of each transaction as executing by itself.

Concurrency is achieved by the DBMS, which interleaves actions (reads/writes of DB objects) of various transactions.
Each transaction must leave the database in a consistent state if the DB is consistent when the transaction begins.

DBMS will enforce some ICs, depending on the ICs declared in CREATE TABLE statements.
Beyond this, the DBMS does not really understand the semantics of the data. (e.g., it does not understand how the interest on a bank account is computed).
Issues: Effect of interleaving transactions, and crashes.
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Each transaction must leave the database in a consistent state if the DB is consistent when the transaction begins.

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