The DBA and PhD are both doctoral research degrees, but are designed for different purposes.
The PhD offers those with ambition to move into academia and become a professional researcher the means to do so. A DBA on the other hand is a professional degree, designed to support you and give you with the skills you need to deliver unique solutions, based on accurate un-biased analysis of a situation in your sector or organisation.
The average time needed to complete the DBA and PhD programme is 5 years. There is no fixed start date; you can begin at any time.