The T-System is where hero data is stored, and is the most well-protected part of Hero Factory. If the entire building was completely destroyed, The system would not be scratched.
Why is it so well protected piece of equipment? Because it is where heroes are recreated. This facility basically recycles killed heroes. The big challenge is they can only revive heroes within 24 hours.
Mr. Makuro knew that it would be horrible to cease existing (at least completely) after death, so he created the T-system to resurrect fallen heroes. Iron Kriko once tried to destroy the thousand-trilabyte info machine but got captured and cuffed by Cuffy probe.
The T-System played a large roll in the Breakout as well, during which many heroes were killed off by the villains they battled. These same villains often required heroes with upgrades or an entire Hero Team to take down.