What will happen if concurrency control fails?Lost Update ProblemUncommitted dependency (dirty write) problem / Permanent update problemInconsistency analysis problem / Incorrect summary problem

If concurrency control fails, several problems can occur:

1. Lost Update Problem: This problem occurs when two or more transactions select the same row and update the row based on the value originally selected. Each transaction is unaware of other transactions, so the last update overwrites updates made by the other transactions, which results in "lost updates".

2. Uncommitted Dependency (Dirty Write) Problem: This problem occurs when one transaction updates a database item and then the transaction fails for some reason. The updated database item is accessed by another transaction before it is either committed or rolled back. This is called a "dirty read". If the first transaction is rolled back, the second transaction will have read an item that is considered to have never existed.

3. Inconsistency Analysis Problem / Incorrect Summary Problem: This problem occurs when multiple transactions are executing concurrently, and the output of a transaction is used by another transaction. The problem here is that the second transaction is unaware that the first transaction is not yet committed to the database. If the first transaction fails, the second transaction will have incorrect data.

In summary, the failure of concurrency control can lead to data inconsistency and system unreliability. Therefore, it is crucial to ensure effective concurrency control in a database system.