He said a number of key pieces of work were being advanced as part of achieving this permanent, robust solution.
Mr Lees said the full recovery was expected to take "some months".
"We continue to move quite cautiously as while our systems are all working, we are realistic about the possibility of further failures in the systems."
Planning for the recovery phase is under way.
The fire early on Monday in the DHB's main computer server room on the Rotorua Hospital site caused a major outage affecting computer and patient management systems, along with email and internet access for three full days.
Rotorua and Taupo Hospitals and the DHB's community services reverted to manual systems, and patients were warned to expect delays.
Chief executive Ron Dunham said the last few days had been difficult and he was proud of how all staff had worked to ensure patients were safe and cared for during the outage.
He said they were grateful for the strong support and help from neighbouring district health boards, service providers and primary care, during the outage.