A-Atomicity
C-Consistency
I-Isolation
D-Durability
Atomicity Means that each transaction is treated as all or nothing.that is either is committed or aborted.
Consistency ensures that a transaction wont allow the system to arrive at an incorrect logical state.The data must always be logically correct,means all the rules and constraints in the system are honored even in the event of system failure.
Isolation separates concurrent transactions from the updates of other incomplete transactions.
After a transactions commits,the durability property ensures that the effects of transaction persists even if a system failure occurs.
2.What are Lost Updates?
Lost updates occur when two processes read the same data both manipulate the data,changing its value, and then both try to update the original data to the new value.the second value might overwrite the first update completely.
3.What are dirty Reads?
Dirty Reads Occur when a process reads a uncommitted data.if one process has changed the data but not yet committed the change, another process reading the data will read it in an inconsistent state.
4.What are Nonrepeatable reads?
A read is nonrepeatable read if a process might get different values when reading same data in two separate reads within the same transaction.
5.What are Phantoms?
A phantom occurs if a select operation using a same predicate in the same transaction returns a different number of rows.
