Number of simultaneous connections

This specifies the total number of connections that are made from your system to whois servers. Some whois servers impose a limit on number of simultaneous connections that are allowed.  If you find that connections are being refused decrease this number to a lower value.

Connection Interval

Specifies the gap between two sets of connections.  Increase this if you get too many errors.

Tip: When you have a large number of domains in the database the software may become slow and sluggish whenever multiple lookups are in progress. Increase the connection interval to a large number if this happens.

Rescan Interval

After a domain is looked up the date and time of lookup are saved into the database (in the Last Checked At field).  The rescan interval parameter specifies the minimum interval that should elapse before another lookup can be performed for that domain.

You can normally leave this at 720 minutes (default).  If you want to lookup a single domain (overriding the rescan interval setting) select the domain and then use the "Lookup Selected" option.

The "Multiple Lookup" option will always make use of the rescan interval.