hii bro yours video is just awesome to understand new concept of dbms. i am very much attracted to your presentations.. i like to know wt kinda appln you are using to make this video.
@ time 5:20 , you said we have to downgrade the lock from exclusive to share to read... ok but in previous lecture (last example T1 : A --> B) you said exclusive lock is used to read as well as write. What does it mean?
Because when there is a exclusive lock placed on the data element by a transaction, and another transaction request a shared lock to read the data element the request will not be granted. Because write and read are conflicting operations. Thus we down grade the lock to shared lock (read operation) because read-read are not conflicting.
Dheer Varyani cascading rollback is definitely possible because.. assume a transaction lock some data item and perform operation and then unlock it in second phase thus making it available to be used by some another transaction but then transaction first fails and rollback.. this lead to cascading rollback of second transaction too as it uses data that has been modified by transaction one... Hope you understand
sir, in previous lecture you have said that if there exist exclusive lock on a data item,then we can not use shared lock on this same data item ..but here you are useing it in " lock upgrade /downgrade" part ....i am confused ......please explain ...
He is giving arbitrary locking examples. You can never apply any lock on a pre existing exclusive lock unless the lock has been removed. Hope this helps
Love your videos. Thank you for making the Advance Database Systems class I'm in a little bit easier!
Im watching all ur videos for serializability. You are the best man! Thanks a lot :)
thank u very much for these wonderful videos
Thank you so much, your explaination is simple and easy to understand!
thanx sir.... your video is better than boring class lectures...
very well explained, you helped me understand the subject, thank you very much.😀
ok
This video helped me very much understanding the subject. Thank you.
May I Know what is the software you are using to teach?
Sir , only cz of u ..I cleared my concepts . Thanx a lot sir :-)
Very well explain..
Very well explained. Thanks!
Very good
hii bro
yours video is just awesome to understand new concept of dbms. i am very much attracted to your presentations.. i like to know wt kinda appln you are using to make this video.
@ time 5:20 , you said we have to downgrade the lock from exclusive to share to read... ok
but in previous lecture (last example T1 : A --> B) you said exclusive lock is used to read as well as write.
What does it mean?
Because when there is a exclusive lock placed on the data element by a transaction, and another transaction request a shared lock to read the data element the request will not be granted. Because write and read are conflicting operations. Thus we down grade the lock to shared lock (read operation) because read-read are not conflicting.
What’s the software used for writing…
Thank you for the video my beautiful friend :)
you should have given an example on cascading rollback happening, when 2PL is used
here's a good explanation
ruclips.net/video/L_JsPRORLfo/видео.html
here you are upgrading and downgrading on data under same transaction,and in the previous video it was on different transactions@subhajit khan
How is cascading roll back possible in simple 2pl please give examples!
Dheer Varyani cascading rollback is definitely possible because.. assume a transaction lock some data item and perform operation and then unlock it in second phase thus making it available to be used by some another transaction but then transaction first fails and rollback.. this lead to cascading rollback of second transaction too as it uses data that has been modified by transaction one...
Hope you understand
sir, in previous lecture you have said that if there exist exclusive lock on a data item,then we can not use shared lock on this same data item ..but here you are useing it in " lock upgrade /downgrade" part ....i am confused ......please explain ...
here you are upgrading and downgrading on data under same transaction,and in the previous video it was on different transactions@subhajit khan
He is giving arbitrary locking examples. You can never apply any lock on a pre existing exclusive lock unless the lock has been removed.
Hope this helps
anyone up here in 2018
Aditi Dede no