SQL Server Locks Interview Question:

Explain the various types of concurrency problem. I.e. Lost or buried updates, uncommitted dependency, inconsistent analysis, phantom read?

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Types of concurrency problem:-

Lost or buried updates: - When the same row is selected for updates by two or more transactions and updates the row based on the value originally selected. Here, each transaction is unaware of the other transactions. The last update overwrites updates made by the other transactions, which results in lost data.

Uncommited dependency: - here, a transaction reads data of another transaction which has not been committed yet. The value may be changed by the other transaction.

Inconsistent analysis: - here, the transaction reads the data inconsistently. This means that every time the data is read; different values are read. This is because another transaction is continuously updating the data.

Phantom Read: - Here, an insert or update is done on a row that belongs to some other transaction. Hence the transaction may read a row that may be deleted by some other transaction.
Submitted by: Administrator