The data management plan is a tool used to ensure well thought-out and sound work with research data. The plan should be a living document that can develop and evolve.
The purpose of the plan is to provide support early in the research process in order to avoid future problems with data management. Many funding agencies now require a data management plan at the time of application.
The data management plan is important for those who in the future wants to access or review produced research data and not only an internal document. You can always complete the data management plan by adding a "read-me" document for more thorough description on data management procedures.
Templates for the data management plan is available at the different schools. Always check with the funding part if there is any specific information they want to add to the plan!