Dirty reads-problems of concurrent transactions, Database Management System

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Dirty Reads: T10 reads a value which is updated by T9. This update has not been committed and T9 aborts.

T9	T10	Value of x old value = 200
T9	T10	T9	T10
UPDATE X		500
	READ X		500
ROLLBACK		200	?

Here T10 reads a value that is updated by transaction T9 that has been aborted. Therefore T10 has read a value that would never exist in the database and hence the trouble. Here the difficulty is primarily of isolation of transaction.

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