You can turn on ticket archiving to trim down the number of tickets that appear in the service desk.
This will help optimise the helpdesk database.
To turn on Ticket Archive:
Go to: Service Desk | Configuration | Settings | Ticket Archival | Tick Enabled | Click Save. Configure the schedule to allow ticket archival to occur on a regular basis.
A new option under the Service Desk menu will appear called Archive where the archived tickets will be listed.
For each queue, go to: Service Desk | Configuration | Queues | choose a queue, scroll down to Archive Preferences and configure the Archive closed tickets older than: setting and the Delete archived tickets older than: setting.
To archive a ticket individually and manually:
Select the ticket from the ticket list (by ticking in the box next to it). Click Choose Action | Archive
The ticket will be moved from the Tickets section to the Archive section.