AutoCAD is running out of system memory

I am using AutoCAD for a couple of years. Today I got this error message for Low Memory. The complete error message you can see in the following attached image. Does anybody know how this error can remove? Please let me know. Thanks.

AutoCAD – Low Memory
AutoCAD is running out of system memory. Continuing the current command may result in program failure or loss data. Do you want to cancel the current command?
