Catalyzes DNA synthesis. Acquires processivity by associating with a heterodimeric processivity factor comprised of the viral A20 and D4 proteins, thereby forming the DNA polymerase holoenzyme. Displays 3'- to 5' exonuclease activity. Might participate in viral DNA recombination. Does not perform translesion synthesis across an abasic site (By similarity). a 2'-deoxyribonucleoside 5'-triphosphate + DNA(n) = diphosphate + DNA(n+1) Interacts with A20. Component of the Uracil-DNA glycosylase(UDG)-A20-polymerase complex; A20 and UDG form a heterodimeric processivity factor that associates with E9 to form the processive polymerase holoenzyme (By similarity). Belongs to the DNA polymerase type-B family.