Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
Lost Updates: Suppose the two transactions T3 and T4 run simultaneously and they happen to be interleaved in the following way (suppose the initial value of X as
10000):
T3
T4
Value of X
READ X
10000
SUB 5000
5000
ADD 3000
13000
WRITE X
After the implementation of both the transactions the value X is 13000 whereas the semantically correct value should be 8000. The trouble occurred as the update made by T3 has been overwritten by T4. The root cause of the trouble was the fact that both the transactions had read the value of X as 10000. Therefore one of the two updates has been lost and we say that a lost update has occurred.
There is one more way in which the lost updates can happen. Consider the following part of some transactions:
T5
T6
Value of x originally
2000
UPDATE X
3000
4000
ROLLBACK
Here T5 & T6 updates the similar item X. After that T5 decides to undo its action and rolls back causing the value of X to go back to the original value that was 2000. In this case also the update performed by T6 had got lost and a lost update is said to have happened.
Q. Explain the terms key constraints participation constraints and mapping caradinalities in ER model. Participation Constraints : The participation of an entity set E i
usecase diagram,activity diagraM,SEQUENCE DIAGRAM
In an organization several projects are undertaken. Each project can employ one or more employees. Each employee can work on one or more projects. Each project is undertaken on the
how many hourse have been spent on a certain project
In case of entity integrity, the primary key may be declared? In a case of entity integrity primary key may be not Null.
In this assignment, you will create a program that works with multiple tables. In this assignment, you will work with the factory and sales tables. 1. Create a new project nam
Update or Modify operation alters the existing values. If these operations alter the value that is the foreign key also, the only check need is the similar as that of the Insert op
Insulation between conceptual and physical structures It can be defined as: 1. The Database Administrator should be capable to vary the storage structures without affectin
Example : Create a sequence named SEQSS that starts at 105, has a step of 1 and can take maximum value as 2000. CREATE SEQUENCE SEQSS START WITH 105 INCREMENT BY 1 MAX VA
Find the names of all Albums that have more than 30 tracks. Result: (name: varchar(255))
Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd