Support Concurrent Update

Presented by: MATAAC, Gladys G.

Concurrent Update

• occurs when multiple users make updates to the same database at the same time.

The Concurrent Update Problem

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Batch Processing

Batch Processing

• processing technique in which a single update program reads the batch of records in this file one at a time and erforms the appropriate updates to the database.

Two-Phase Locking

• Locking- denies ither users access to data while the DBMS processes one user's update to the database

Two-Phase Locking

• Two-Phase Locking- approach of handling locks where the DBMS hold locks until it completes all the updates in the transaction.– Growing Phase- fist phase in which the

DBMS locks more rows and releases none of the locks.

– Shrinking Phase- second phase in which the DBMS releases all the locks and acquires no new locks.