Where and how can I change the frequency of survey being sent out
There is a trigger called "tps_survey" under the table im_incident which will need to be amended. Open that up and there is a line you need to edit to change to the frequency you want (it is clearly marked out in the trigger and marked as red below):
declare @constant int
select @constant=10 -- amend this value to change frequency of survey
declare @pm_lifecycle_guid uniqueidentifier
Please ensure this is done by your DBA and a backup of the database is done before making any amendments on your database. Where possible please ensure it is tested on a test system before applying it to your live environment.