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Research Note Topic:
Research Note Description:
CONCURRENCY IN DATABASES :
In my opinion this term means that there are many transations made to access the same database at same time.It means that there are n number of transactions at a time on same database.For example, lets take our my students database which anybody can easily use to make transactions at a time.By transactions what i intend to mean is the data entry done by the users.In a huge database some
concurrency control mechanism
is required to prevent the
from interfering with one another.
The problems faced when there is no concurrency control are:
1. Lost update.
2. Uncommited dependency.
3. Inconsistent Analysis
These problems arise as time schedule are not
-i.e., not equivalent to some serial schedule involving the same transactions. The most used approach for solving such problems is by
.There are two basic types of locks,
.These locks ensure serializability.This is done by acquiring an S lock on everything updated and acquire an X lock on things updated, and keep all locks until end-of-transaction.A serializable schedule implies that if A and B are any two transactions in a schedule, then eiher A can see B's output or vice versa.This protocol can lead to a
which can be removed by removing all of its locks.
Prof. Ashay Dharwadker