What Is Windows 7 Backup Error 0x81000019?

I am using my system for two years from now. Nowadays, when I am trying to back up my computer, it is showing Windows-7 backup error code 0x81000019. The description says a shadow copy creation is not possible, check VSS and SPP application. It’s about space issues, but I have enough space in my system. What can I do now?

