Before doing any upgrade or update of an SAP system you need to take the backup of the Database , You can do this using BR tools for oracle. Below are the step-by-step screenshots to take the backup.
You need to login with ora<SID> User , you need to run the commands brtools , then it will give you a menu to choose the options.
You need to shutdown the database to take the offline backup
All the backup files will be saved in the location oracle/SID/backup/*