The Deployment Image Servicing and Management (or DISM) tool is used to repair the files SFC uses to check your system.

Microsoft advises this be run before SFC in Windows 8 or newer.

In an open console session (like in Step 1) type dism /online /cleanup-image /restorehealth. This compares against an online image from Microsoft to perform repairs.

A progress bar will show in the console window and indicate when complete.

Run SFC, especially if the first run through indicated it could not repair all corruption. DISM may have replaced the files that were previously damaged

Check your syntax closely. Spelling, spacing and punctuation all matter here) Incorrectly typed commands will often result in an Error 87.