Photoshop: Scratch Disk Full
The Unger IT Department Knowledgebase
Photoshop: Scratch Disk Full
Specify appropriate drives for scratch disk
By default, Photoshop uses your internal OS drive as the scratch disk. If you have more than one drive or partition, make sure to select the fastest drives with maximum free space as your scratch disk(s). You can also resolve a 'scratch disk full' condition by selecting additional drives for use as scratch disks.
Hold down the Cmd + Option keys (macOS) or Ctrl + Alt keys (Windows) during app launch and set a new scratch disk for your system under the Scratch Disk Preferences dialog that opens.
Specify appropriate drive for scratch disk.