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May be an image of text that says 'In context of database, let Τι and T2 are two concurrent transactions. Consider the following sequence of operations on data X: T1: READ(X) T1: WRITE( This is a (1) Dirty Read (2) Lost Update (3) Incorrect Summary (4) Unrepeatable Read T2: READ(X) T2: WRITE(X'           

order of  operations T1T2T1T2                                                                                           

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2) Lost Update Problem

 

Lost update problem: 

 

This problem occurs when two transactions that access the same database items have their operations interleaved in a way that makes the value of some database item incorrect. Suppose that two transactions are submitted at the same time and their operations are interleaved, then the final value of the item X is incorrect because transaction T2 reads the value of X before T1 changes it in the database and hence the updated value resulting from T1 is lost.

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