3Com 3C15500 - Network Director User Manual page 311

Configuration 307
Figure 144 Logging Tab of Tools > Options Dialog Box
Increasing or decreasing the time period will preserve any existing data
already collected for each monitor. Increasing the time period will cause
existing history data to be retained for longer. Decreasing the time period
will discard any excess data.
If you do not wish to maintain monitor histories at all then you can
uncheck the checkbox for the Maintain monitor history for: setting.
3Com Network Director will then only keep the two most recent monitor
states for each monitor.
Decreasing the time period for which history is maintained will reduce the
memory used by 3Com Network Director on your PC. You may wish to
decrease this time period if you find that 3Com Network Director is
running slowly, or is using too much resource on your PC.