SR cannot and Should not do the secondary maintenance as per railway board regulations. The rake receives maintenance before starting as mail to Chennai. So SR can provide only OEA ( Other End Attention) to Bangalore Mail. It means SR should clean the coaches (activities like sweeping, cleaning restrooms and watering the coaches). For these activities, its not necessary to take the rake into the yard, it can be done in PF or in stable lines like in Chennai Beach or Korkkupet or Tondiarpet. The rake criteria for LHB to get secondary maintenance is if the rake's Route kilometers exceeds 4000 kms.