Is DB2 more reliable and stable compared to PostgreSQL or MySQL? Always i was using MySQL or PostgreSQL for my projects such as Web/Desktop apps.
I had data loss few times and thanks to old backup i was always up and running. 

But for a recent project for Airport, i have to use something which never ever can lose its data at-least not database until it has power in the circuit..

So i am thinking DB2 should be the best for such risk less missions? Any idea or hints.

Thanks in advance.
All of the platforms you have mentioned can run close to zero data loss configurations. All of them could be deployed in a configuration that will fail.

Platform choice is one part of the puzzle. It will be your implementation of the platform that determines whether or not your requirements are met.


MySQL Cluster
Oracle RAC
PostgreSQL High Availability
SQL Server High Availability


In reality, high availability and disaster recovery are a trade off between uptime, Recovery Point Objective, Recovery Time Objective and cost. 

Zero data loss and zero downtime is expensive, complicated to setup and complicated to maintain. There is no free lunch.