there are two ways that I know where workbooks can lose db credentials. Are either of these the case?
- When workbooks are published, the user publishing them should always remember to embed credentials instead of requiring a prompt
- On server, if ownership is transferred to another user, then credentials will be lost. Go vote this idea up: https://community.tableau.com/ideas/6698
There's one other way embedded credentials can be lost: Tableau Server software update.
It appears random, doesn't happen to the same workbooks, but I and some of my users have experienced workbooks switching from Embedded to Prompt after a Server version update. I've also had some people lose their Publisher role after an update. Both instances of it happening are very small (maybe 0-4 objects after a version update).