Since publishing the FDA Process Validation Guidance in 2011, the FDA regards process validation as a three-step lifecycle with the phases
Meanwhile, the process validation lifecycle model is state of the art in the EU, as well (revised Annex 15 of the EU GMP Guideline). The new part about the lifecycle model was step 3 (Continued Process Verification or Ongoing Process Verification, as it is called in the EU), which causes some companies problems with the implementation. The FDA however puts great emphasis on this step 3, as it stated in a Warning Letter to an Indian pharmaceutical manufacturer. Under the caption "Process Control", the FDA criticises that the company has no adequate, ongoing program for monitoring the process in order to show the stability of the manufacturing process and therefore the constant quality of a drug product. It explicitly refers to a link which leads to the FDA process validation guidance.
For further details please read the FDA Warning Letter to Hetero Labs Limited on the FDA Website.