I use keepass Version 2.24 and I have a little question. Is the complete database encrypted or only the passwords? I often use the "notes" field to store additional secret data. So I wonder if it's save to store this kind of data in the comments field.
KeePass encrypts the entire database before saving to disk. When the database has been unlocked all unencrypted data is stored in memory and certain data, like passwords, are re-encrypted in memory.
There is more information in the Help pages. http://keepass.info/help/base/security.html
So if the database isn't opened the "notes" field is as save as the "password" field, right?
Correct. The entire file is encrypted in one go.