What could be the solution for this? I am performing a backup of a web application but it doesn't allow me and at last I end up with the below error.
You need to run SharePoint Configuration Wizard so that it will upgrade the content DB to match with the SharePoint binaries' version. SharePoint will work to a certain point when there is a difference in DB vs. binaries version, but at some point the difference is too much and DB is blocked.
Alternative to SharePoint Config Wizard is to run:
It does exactly the same as the graphical SharePoint Configuration Wizard.