Dirty Read

Question

The Transaction : -   

   T1         T2

  R(a)

  W(a)

                 R(a)

   C

                   C

The above shown schedule is not Dirty read Right ?

Answer 1

Of course It is Dirty read. When $T2$ read item $A$, It was written by uncommitted  $T1$. The value of item A that is read by $T2$ is called dirty data because it has been created by a transaction that has not completed and committed yet; hence, this problem is also known as the dirty read problem.

You must be confusing "Dirty read probelm" with "recoverability"... The given Schedule is Recoverable But it has dirty read.

Comments

1. But in this case there won't be a problem at all but still it will be considered as Dirty Read ?

2. If a transaction is free from dirty read then it will be recoverable as well as cascadeless right ?

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2. If a transaction is free from dirty read then it will be recoverable as well as cascadeless right ?

Absolutely. 

But in this case there won't be a problem at all but still it will be considered as Dirty Read ? 

If you don't wear helmet while riding a bike and No accident happens.....doesn't mean it is right to Not wear a helmet. 

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Nice answer sir got it :)

Answer 2

Its dirty read problem because you are reading uncommited data