Standard log tables in Campaign have pre-set retention periods on them limiting their data storage duration, to avoid overloading your system.
Data retention configuration is set by Adobe technical administrators during implementation and values may vary for each implementation, based on customer requirements.
Reach out to the Adobe consultants or technical administrators to learn more about retention periods which apply to your environment, or to set custom retention periods.
Note that using standard workflow functionality, it is possible to set up retention periods for any custom table.
Below are the default retention periods for standard tables. Whenever possible, and depending on your data usage, Adobe suggests you to move to the recommended retention periods to improve performances of your Campaign instance.