Is Dirty read always leads to an Irrecoverable schedule? @pan...

Is Dirty read always leads to an Irrecoverable schedule?

 @panwarrohit :

7Comments
Rohit Panwar @panwarrohit
13 Dec 2019 06:31 pm
@ambikeshkumarsingh it is not always leads to irrecoverable schedule bcz there may be a case when transaction T2 reads whats ever Transaction T1 writes and transaction T1 first commit and then T2 commit.in that case it will be recoverable.
Ambikesh Kumar Singh @ambikeshkumarsingh
13 Dec 2019 08:11 pm
@panwarrohit So you are saying that "If the order in which dirty read is happening, in the same order if commit or abort operations are performed then there is a chance that Schedule maybe Recoverable".
SHIVAM KUMAR @shivamkumar12
13 Dec 2019 08:55 pm

@panwarrohit

NO

IRRECOVERABLE schedule happening only when if Tj is reading , write and commited the value of Ti which is still not commited , and if Ti is abort then Ti should be RollBack . but now Tj can't Rollback because its already Committed .

But , in dearty read we can read the value of Ti in Tj but don't commit before Ti . now if Ti abort then you can Rollback both Ti & Tj . so, it's Recoverable Schedule . Hence Dirty Read not always lead to irrecoverable Schedule .

Best reference : https://www.geeksforgeeks.org/recoverability-in-dbms/

Ambikesh Kumar Singh @ambikeshkumarsingh
16 Dec 2019 02:04 pm

I am trying to say that "let us say there are three transactions T1, T2, T3 and if T2 is reading an uncommitted value from transaction T1 and T3 is reading an uncommitted value from transaction T2:

In this scenario the dirty read pattern or order is T1 -> T2-> T3

and if commit order  is the same as:                        T1 -> T2-> T3

then the schedule is recoverable even though it seems irrecoverable at the beginning because the later transactions have a chance for rollback.

@panwarrohit

Rohit Panwar @panwarrohit
17 Dec 2019 01:35 am
if later T1 commit then T2 and then T3 at that time it will be recoverable.but if you dont know about commit then it may be case that t2 commit before T1 commit
Ambikesh Kumar Singh @ambikeshkumarsingh
17 Dec 2019 03:50 pm
@panwarrohit sir, So can we say that in a generalized statement that dirty read always not lead to irrecoverable schedule if nothing is mentioned and simply this statement is given?
Rohit Panwar @panwarrohit
20 Dec 2019 02:52 am
yes

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