Protected session timeout is a time period after which the protected session is wiped out from browser's memory. This is measured from the last interaction with protected notes.
History snapshot time interval is time in seconds after which new history record will be created for the note.
This action will create a new copy of the database and anonymise it (remove all note content and leave only structure and metadata) for sharing online for debugging purposes without fear of leaking your personal data.
This will remove all image data of images not used in any current version of note from the database (metadata will remain). This means that some images can disappear from note history.
This deletes all soft deleted rows from the database. This change isn't synced and should be done manually on all instances. Use this only if you really know what you're doing.
This will rebuild database which will typically result in smaller database file. No data will be actually changed.