Importance of Historical and Warranty data:

Every company gathers and maintains data regarding current production. Some are stored databases and some in form of hard copies.
Now question is what data is stored and how they are classified?
Some companies store data of the product since its manufacturing process. If there is any issue during the process of manufacturing, its logged for further action.
Say you are machining a part and there is issue with surface finish, then you would log the issue.
There is other issues that you log, which are from early testing before the final product is shipped to sell. These failure called Very Early Hour failure also called premature failure. This is premature failure, which is mostly to do with incorrect manufacturing/ Assembly. These issues are logged with a different name to ensure resolution of issues on the manufacturing floor.
Rattling and vibrations caused during the normal operation of the product can be traced back to loose assemble or loose screws.
The third failure is repairs during product life time. This is also called product life expectancy. These are calculated on the bases of frequency of repair while product is still under warranty. This is mostly considered as incorrect design or design failure.
The issues related with failure of one of the components in the product leading to final product failure is attributed to design failure.

How does this data help?
The data gathered while manufacturing the process is gathered and addressed in PFMEA. The suggestions are added in the control plan and work instructions are updated. The same is the case in terms of premature failures. The failure modes are addressed in the PFMEA and control plans and work instructions are updated.
The failures that occur in the period of warranty is first recorded and sorted in order to resolve issues on the basis of severity, frequency and cost of failures. This issues based on the impact get assigned with a black belt project.
This data is also helpful when you are designing a new product as you can have lessons learned or maybe resolve them using design for upcoming product. This also helps lower warranty on exiting production and also improves reliability on the upcoming and new product.