A network-related or instance-specific error For Central Administration sharepoint

Error

A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified).

Resolve Step:

1- Open SharePoint Central Administration v4 Web.config file in VS2010 or notepad.

2- Find this Node.