Hello,
If you have uninstall sep client but host name not delete SEPM console your licenece not free.
if you have delete host name in SEPM console,Your particular license will be free and you can use another system.
Configure SEPM to remove clients which have not connected within a specific number of days.
- Open SEPM and select the Admin panel.
- Click on Servers
- Right click on the Site where your management servers are located and choose Edit Properties
- Check "Delete Clients that have not connected for __ Days"
- Enter a value for Days.
- Click OK.
SEP 12.1
http://www.symantec.com/docs/TECH176400