Setting: URLM_MAX_LOG_LINES

  Maximum number of URLs to keep in the log. May be set to zero to
  disable trimming by length (in which case, trimming by age may still
  be used or not, as desired).

  When set to non-zero, the log will be trimmed to this size by discarding
  older (lower-numbered) URLs. See below for explanation of when trimming
  is done.