Since SharePoint Foundation 2010, patching SharePoint is a two-step process. The updated binaries are first installed and then PSCONFIG must be completed to update the SharePoint databases. 
Without completing PSCONFIG, you might experience unexpected SharePoint search failures and all backups may stop working on the affected server.
 

You can run the following commands to determine if you need to complete the update process with PSCONFIG:

  • Launch an elevated (Run as Administrator) SharePoint 2010 Management shell from start, All Programs, Microsoft SharePoint 2010 Products, SharePoint 2010 Management Shell.
  • Once the shell opens, type the following command followed by enter:  
    (get-spserver $env:computername).NeedsUpgrade

In order to update the SharePoint databases, you must manually run the PSconfig utility. To run the utility:

1. Open an Administrative command prompt.  
2. Change directory to C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\BIN  
3. Run PSConfig.exe -cmd upgrade -inplace b2b -force -cmd applicationcontent -install -cmd installfeatures