Will my EDM indexes still work after I upgrade my DLP detection servers?
Yes, EDM indexes can be copied over to the new version, for example 15.8 > 16.0, of the same installation; i.e. if 15.8 was upgraded to 16.0 and you still have 15.8 EDM indexes available.
EDM should still function after the upgrade.
However, it is highly recommended to re-index all of the EDMs as soon as possible after the upgrade.