if db crashses then how we recover backup and log file with proper reason Please.
I don;t understand what are you trying to say by this statement..
/* How we recover backup and log file */
Sorry we don;t recover backup and log files..
But yes with your given scenario if i understood it well we can recover your database with no data loss because you did n't metioned any timelines for recovery.
Any Change you make in the database is considered as a transaction and hence it is written in you active transaction log file. So as you mentioned if your log backup are running normally then you can most definitely recovery your database and also all data files and log files will be there...
Going forward pls make sure that you are mentioning your problem more clearily.
I hope the reply will help you..