Check data integrity
From LimeSurvey Manual
General
The Check data integrity function checks the consistency and the redundancy of data. It can be accessed from the Configuration dialog:

Data consistency check
It looks for possible errors that might exist between the response tables and survey tables or between the token list and the CPDB, ...

All the values from the screenshot need to meet the consistency standards.
Additional parameter for response table field checks
Starting with version 6.x you can set an additional parameter to the integrity check URL named checkResponseTableFields. Just add the following text to the URL: ?checkResponseTableFields=y and press enter. If you set this parameter an additional check will be executed, which checks if all fields in all response tables have correct names, which can take a long time to complete.
Data redundancy check
If you deactivate a survey, the token tables, the response tables etc., will not be automatically deleted. They will get stored in archived tables. If you do not need them anymore, use the Check data integrity function and select the "leftovers" you wish to delete:

