Here is the list to show Oracle oratab location in some operating systems.
|Operating System||oratab Location|
|Windows||In Windows, there's no such oratab, because it uses registry to keep all necessary information about Oracle database(s). Please refer to Oracle Software Registry (regedit)|
Let's see an example of oratab in Linux.
[oracle@test ~]$ cat /etc/oratab
Database servers of a newer RAC system may not contain useful information in oratab because OCR already has it.