What is the meaning of the PBIRS.OLD folder?

[giwi]

Hi,
when i upgrade PowerBI RS (OnPrem), the previous Version is stored in C:\Program Files\Microsoft Power BI Report Server\PBIRS.OLD. Is ist possible to switch back to this Version when i restore the sql database too?
I never tried before but the upgrade document describe for example, that some files should be backup (see https://docs.microsoft.com/en-us/power-bi/report-server/upgrade#backing-up-the-configuration-files)

But why should i backup the files when it´s already store in PBIRS.OLD Folder?

Thanks for helping/solution
Best regards
Wilfried

[d_gosbell]

The big problem I've seen with PBIRS.OLD is firstly that I do not believe it is documented, so it may not always be available in the future. Therefore it's safer to make sure you have a manual copy of the configuration files. 

The second issue I've seen is that most people's inital response when they get an error while installing an update is to try re-running the installer. This then overwrites PBIRS.OLD and if your config files have been corrupted you then have to re-create them from memory.