To improve your data collection performance, it is important to know how to manage your existing ranges under Admin > Data Collectors > Ranges. If you are not using a set of ranges anymore, it is important to delete the unused ranges.

Exclude or Delete
You have 2 options, either to Exclude or to Delete a range; deleting an unused range will remove it from the set of ranges to reference, therefore improving the performance.

• Exclude - The exclude option is a way to exclude a specific IP address, or ranges of IP addresses, for other ranges that are defined and being collected from. Even when a range is Excluded the Data Collector still pings and acknowledges that range, taking time during the data collecting intervals.
• Delete - Deleting ranges removes them from the server to reference, reducing the time the server is requesting information from data collectors.

Deleting a Range:
Go to Admin > Data Collectors > Ranges
Locate your unused Range
Select the 'Delete' option 
Confirm the option to delete the range

Deleted a Range - What about the data from that range?
As a range is deleted from the list under Admin > Networks, its only telling the servers that it is not going to bother looking for those ranges anymore. The information already collected from those ranges in the past, will still be part of the data set in your account. The information is part of all collected history.