File/Secure Mode...
For those with stringent security requirements, QS provides a strong encryption Secure Mode. When in secure Mode, the QS database is encrypted between sessions. At the start of a session the database is decrypted into memory and never saved to disk in unencrypted format. Also, notable, the method QS uses to place the database in memory locks the db there so it won't be swapped to the windows pagefile. I wish I could say, beyond the shadow of a doubt, the memory will never be swapped to disk, but the inner workings of windows leave this question somewhat iffy. I've done what I can. The unencrypted database remains in memory until the program is closed when the entire file is PGP encrypted as it is saved to disk.
The format of the unencrypted database is proprietary and makes use of compression to obfuscate the data contained. This means that should the data end up in the pagefile, it strongly resembles random data and would likely prove difficult to locate or access.
As I've mentioned before in this documentation, for the ultimate in security, you can download the full version of Eraser for free from their their website, online: Eraser Home Page, and do periodic wipes of the windows freespace and pagefile. Eraser is the highly-regarded secure file deletion software QS uses to wipe temporary files ceated during the encryption process. For more on this topic, see: More on Secure Deletion.