viewquestions/12461/What is the need for normalizationDatabase Management Systems 10CS54 VTU notes JUNJULY 2013Jan 2016

The Eduladder is a community of students, teachers, and programmers just interested to make you pass any exams. So we solve previous year question papers for you.
See Our team
Wondering how we keep quality?
Got unsolved questions?

Ask Questions
Database-Management-Systems---10CS54-VTU-notes-->View question


. Write a short Notes Database Management Systems - 10CS54 VTU notes (Dec /Jan 11/Jan 2016)

a) 2PL Lock: 



By:anonymousguy7799

Taged users:


Likes:
Be first to like this question

Dislikes:
Be first to dislike this question

Talk about thisDelete|Like|Dislike|


Answers

a) 2PL Lock: Locking is an operation which secures
(a) permission to Read or (b) permission to Write a data item for a transaction. Example: Lock (X). Data item X is locked in behalf of the requesting transaction.
 Unlocking is an operation which removes these permissions from the data item. 
Example: Unlock (X). Data item X is made available to all other transactions. Lock and Unlock are Atomic operations. Two locks modes (a) shared (read) and (b) exclusive (write). Shared mode: shared lock (X). 
More than one transaction can apply share lock on X for reading its value but no write lock can be applied on X by any other transaction. Exclusive mode: Write lock (X). Only one write lock on X can exist at any time and no shared lock can be applied by any other transaction on X. Lock Manager: Managing locks on data items. Lock table: Lock manager uses it to store the identify of transaction locking a data item, the data item, lock mode and pointer to the next data item locked. One simple way to implement a lock table is through linked list.  

Nikhil-bharadwaj

Likes:
Be first to like this answer

Dislikes:
Be first to dislike this answer
Talk about this|Once you have earned teacher badge you can edit this questionDelete|Like|Dislike|
------------------------------------

Can you help us to add better answer here? Please see this



Not the answer you're looking for? Browse other questions from this Question paper or ask your own question.

Join eduladder!