Please help us help you and fill where relevant:
Your LimeSurvey version: LS 3.28
Own server or LimeSurvey hosting: Own
Survey theme/template: NA
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I have an existing production version of LimeSurvey that I'd like to shift to it's own subdomain (eg survey.mydomain.com)

This would make it easy to shift between another install on the same server already had it's own subdomain. The use case is to control for LS updates basically and/or having a test versus production environment.

Is it possible to shift an existing install to a subdomain without breaking to much or is it necessary to do a fresh install?

Thanks!
 

Easy, no DB update to do.

Thanks Denis - I guess it breaks links to existing surveys
eg
original mysite.com/subdir/index.php?r=survey/index&sid=X
new survey.mysite.com//index.php?r=index&sid=X

But that's to be expected

Yes like if you move to another domain …