Only a juvenile who is (i) adjudicated delinquent of an act enumerated in subsection B or C of § 16.1-269.1 and is 11 years of age or older or (ii) 14 years of age or older may be committed to the Department of Juvenile Justice. In cases where a waiver of an investigation has been granted pursuant to subdivision A 14 or A 17 of § 16.1-278.8, at the time a court commits a child to the Department of Juvenile Justice the court shall order an investigation pursuant to § 16.1-273 to be completed within 15 days. No juvenile court or circuit court shall order the commitment of any child jointly to the Department of Juvenile Justice and to a local board of social services or transfer the custody of a child jointly to a court service unit of a juvenile court and to a local board of social services. Any person sentenced and committed to an active term of incarceration in the Department of Corrections who is, at the time of such sentencing, in the custody of the Department of Juvenile Justice, upon pronouncement of sentence, shall be immediately transferred to the Department of Corrections.