Plays a role in processing non linear or branched viral DNA intermediates in order to promote the production of mature packaged unit-length linear progeny viral DNA molecules. Exhibits endonuclease and exonuclease activities and accepts both double-stranded and single-stranded DNA as substrate. Exonuclease digestion of DNA is in the 5'-> 3' direction and the products are 5'-monophosphate nucleosides. Additionally, forms a recombinase with the major DNA-binding protein, which displays strand exchange activity. Degrades host mitochondrial DNA. Forms a complex with the DNA polymerase, the DNA polymerase processivity factor, and the major DNA binding protein (By similarity). Interacts with the host MRN complex composed of MRE11, RAD50 and NBN; these interactions may help in recombination or repair of the viral DNA. Interacts with host MSH6, a component of the post-replicative DNA mismatch repair system (MMR). Produced by alternative initiation at Met-127 of isoform UL12. Belongs to the herpesviridae alkaline nuclease family.