konradh
Thanks,  And where might that be found?

On my daw, it's C:\Cakewalk Picture Cache

Picture cache on my system is C:\Cakwalk Projects\Picture Cache
As a rule I clear it once a month, you'd be surprised how much it fills up and if you have a set limit for it, you will get the disk full error.
 

The path to it is set by default, but in Preferences you can alter the path (if you wanted to).  The data in it are the drawn wave file images for project audio.
 
If the contents of the Picture Cache are deleted, Sonar will recreate the drawn representations of wav data as needed.  Lots of folks clear out the Picture Cache when their playback scrolling starts to lose its smoothness. 
 
The Picture Cache can end up with a lot of data in it - if lots of audio clips are made and then discarded - their drawn waveform data still remains in the Picture Cache.
 
Bob Bone

robert_e_bone
 The data in it are the drawn wave file images for project audio.

FYI, the files in the cache are not image files at all. They are decimated audio files used by SONAR to create clip images.