I missed the hibernate option in Ubuntu 12.04 since its not enabled by default in the system menu. The only option remaining was the suspend option. However, still the hibernate option is available as a command in the terminal.
First its better to check whether its OK to use hibernate command. We need to have equal or higher Swap space in hard disk than our RAM. In my current system, both are 2GB. I checked it from the system monitor application. Since the conditions are preferable, I decided to try the hibernate option. Issue the following command in terminal to hibernate the system.
After entering the password, system will be turned off after few seconds. When I turn it on again, it came back to its last state without any problem. So, I hope everything works fine.