Hey Julia,
OCI has a few different data flows:
OCI DWH - if you are more comfortable with SQL, and you are looking to pull longer term capacity and/or performance data, this is a good option
OCI REST API - if you want to work with OCI's near real time view of your environment, including all the performance samples that OCI stores, this is a good option
OCI's SNMP/Syslog support - if you want OCI to push incident notification as they happen, this may be the glue
So, in my weird role as a generalist OCI SE, I haven't had too many in depth involvements with OCI customers integrating with Service Now as I don't actually "own" specific accounts, but my understanding is that diffferent customers prioritize different goals for their ServiceNow integrations, and some are using multiple data feeds for a best of breed solution.
I will see if I can get some our of PS folks with more familiarity to weigh in
Matt