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!
Two Phase Locking (2PL)
The two-phase locking protocol having of two phases:
Phase 1: The lock acquisition phase: If a transaction T needs to read an object, it wants to obtain the S (shared) lock. If T needs to modify an object, it wants to obtain X (exclusive) lock. No conflicting locks are granted to a transaction. New locks on items can be obtained but no lock can be released till all the locks needed by the transaction are obtained.
Phase 2: Lock Release Phase: The existing locks can be released in any order but no new lock can be obtained after a lock has been released. The locks are held only till they are needed.
Normally the locks are taken by the DBMS. Any legal schedule of transactions that follows 2 phase locking protocol is sured to be serialisable. The 2 phase locking protocol has been confirmed for it correctness. Though, the proof of this protocol is beyond the scope of this Unit. You can refer to more readings for more details on this protocol.
Rules Of Data Normalisation Let us now summarise Normalisation with the help of various clean rules. The following are the necessary rules for the Normalisation process: 1.
Define reference file
There are a number of possible solutions to the open ended brief. One of the simple ones is shown here without the PKs and FKs. It is important to think of how a number of tasks
Define Fifth Normal form is concerned with Ans : Fifth Normal form is concerned with Join dependency.
Adding Redundant Associations for Efficient Access Redundant associations do not add any type of information, therefore during design we should actually examine structure of o
What is a view? Make a view of EMP table named DEPT 20, to display the employees in department 20 and their annual salary. Ans: View is a virtual table that does not consist
Define Deadlock detection If a system does not employ a few protocols that make sure deadlock freedom, after that a detection and recovery scheme should be used. An algorithm
Describe five main functions of a database administrator. Ans: A database administrator (DBA) is a person who is accountable for the environmental aspects of a database. Genera
a need some real life examples of database management systems three level of ANSI SPARC architecture life teacher and student ,company and employee or for NGO etc.
Probelm: a) In the context of OODBMS, define the following terms with appropriate examples. (i) Object class. (ii) Abstract class. (iii) Aggregation. (iv)
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