When setting up surveys, there is a setting for 'Use Stricter Rules' on the Survey Detail page. This article describes what this rule achieves.
CA Service Desk Manager 17.3.X and higher
When 'Use Stricter Rules' is checked on the Survey, Service Desk ensures that a surveyor cannot submit his/her responses to a particular survey that they received more than once.
In such a case if surveyor tries resubmitting his/her response to the survey again, they come across following message:
The following condition was encountered while processing your request to take this survey: ' AHD05245: You already completed the survey. No duplicate surveys are allowed .'
You will not be allowed to complete the survey at this time. Please report this to the Service Desk Administrator.