A DR is a Disciplinary Report, also called an incident report, and it means your boyfriend was written up for a rule violation serious enough to be classified at the felony level internally. That classification is significant because it places the infraction in the most serious category the facility's disciplinary system recognizes.
The specific language "viol. statute felony crime" typically points to possession of contraband that rises to the level of a criminal offense rather than just a prison rule violation. The most common culprits in this category are a cellphone, which became a federal crime under legislation passed during the Obama administration, drugs or controlled substances, or other items on the banned list that carry criminal penalties under state or federal law. The difference between a standard contraband infraction and a felony-level one is that the facility can refer the matter to law enforcement for actual criminal prosecution in addition to the internal disciplinary consequences.
On the disciplinary side, the immediate consequences are predictable. Placement in the SHU, the hole, or disciplinary segregation. That means 23 to 24 hours a day in a cell, limited to no phone access, suspended visitation, restricted commissary, and separation from general population for however long the Disciplinary Hearing Officer determines.
On the criminal side, actual prosecution is not automatic but it is possible depending on what was found and whether law enforcement decides to pursue it. A cellphone used to facilitate outside criminal activity makes prosecution significantly more likely than simple possession.
The most important thing right now is finding out exactly what was found and what charges, if any, are being considered beyond the internal disciplinary process. His attorney needs to know about this immediately if there is any possibility of external prosecution.