Disk Cache

[#1]

Photoshop does not open, because it is low on memory. What should I do?

[#2]

Photoshop does not open, because it is low on memory. What should I do?

[#3]

Please check out these pages: 

https://helpx.adobe.com/photoshop/kb/optimize-photoshop-cc-performance.html

https://helpx.adobe.com/photoshop/using/scratch-disks-preferences.html

If you should have only one disk (and thus no dedicated Scratch Disk) you may have to do some cleaning. 

[#4]

If the message relates to lack of scratch drive space - then you need to free up space on your scratch drive or set the scratch drive settings to use another disk.

You can hold Ctrl+Alt (Cmd+Opt on Mac) during launch to get to the scratch drive set up dialogue.

Dave