tar backup failing, seen error "file changed as we read it" in log files.

Issue

• Observed message “changed as we read it” in log file of tar backup script.

  # grep "file changed" 20150420_bkuptar.log
  tar: /var/spool/mail/root: file changed as we read it
  tar: /var/spool/mail: file changed as we read it
  tar: /var/opt/vgdb10/oracle_dbf/rtcis/redoB/rtcis_redo05_B.log: file changed as we read it
  tar: /var/opt/vgdb10: file changed as we read it
  tar: /var/opt/rtcis/live3/labor: file changed as we read it
  tar: /var/opt/rtcis/live3/log/sqlplus.log: file changed as we read it
  tar: /var/opt/ubkp/data/local/backup_tar_lists/20150420_bkuptar.log: file changed as we read it
  tar: /var: file changed as we read it
  tar: /: file changed as we read it