Removal of ownCloud from CentOS 7 server

My ownCloud is unusable and I can not logon to the administrative functions.

I need to be able to completely remove ownCloud from my CentOS 7.2 vps server and start again with version 9.1
this is due to an upgrade of the server OS, an upgrade of PHP to 5.6, and a total failure on my part to keep track of
ownCloud updates.

i have backed up all files to an external drive and am ready to start fresh with the newest stable version.
i have not found a tutorial or FAQ that mentions removal or re-installation as a solution to my problem
any assistance or instructions will be greatly appreciated

To be able to answer this question the info is missing how the initial installation was done.

i believe the first installation was version 8.1 via the installation wizard (all standard options) and then upgraded to 8.1, as i remember, there was a PHP problem involved in the upgrade.

Have you installed oC via your distros package manager or manually?