Office 365 DLP effectivity

As per article within 1 hour

https://docs.microsoft.com/en-gb/office365/securitycompliance/create-test-tune-dlp-policy

'Your new DLP policy will begin to take effect within about 1 hour. You can sit and wait for it to be triggered by normal user activity, or you can try to trigger it yourself. Earlier I linked to this topic on sensitive information types, which provides you with information about how to trigger DLP matches'

Hope that answers your question!

Best, Chris