Re: 2-Phase locking commit
Acid properties: acid stands for
atomicity
consistency
isolation
durablity
atomicity modification on the data in the database either fail or succeed. The beginning of such a modification starts with a transaction and ends when a transaction finishes (either by a commit or a rollback). A software crash entails an implicit rollback.
Consistency only valid data (valid according to integrity constraints) may be commited.
Isolation one transaction does not interfere with another. The 'executor' of a transaction has the feeling that he has the entire database for himeself.
Durablity a commited transaction will not be lost. For two phase commit and two phase lock u refer
http:// user.it.uu.se / ~arnoldp / distrib / twophase . html
Re: 2-Phase locking commit
Your question is too much theoritical . It is beyond the scope of this discussions to explan all that here. You can easily find all that by little we searching.