Every FinOps question on OCI starts with the cost report. Understanding what is in it saves a lot of confusion later.
What a cost report is
Oracle writes cost and usage reports to an Object Storage bucket, as files you can download. Each row is a line of usage: a resource, in a compartment, using a product during a period, with a cost attached.
The columns that matter most
Service and SKU: what was used, from broad (Compute) to specific (a particular shape or storage class).
Compartment: where the resource lives. This is your main handle for ownership.
Resource identifier: lets you trace a cost to one specific resource.
Region and availability domain: where it ran.
Tags: any cost-tracking tags on the resource, such as environment, owner or project.
Usage quantity and unit: how much was consumed, which is useful when a cost looks odd.
Things that surprise people
•A cost report is a record of what was billed, so it reflects the resource as it was when it was used. Changing a tag or moving a compartment today does not rewrite history.
•Some charges are billed once a month, not every day. If you chart daily spend, these show up as a sudden spike that is not really a change in behaviour.
•Rows with no tags or a generic compartment are common. How much of your spend cannot be attributed is worth tracking in its own right.
Practical advice
Before building any report, decide the three or four questions you want it to answer. Then check that the report actually has the columns needed to answer them. If it does not, fix the tagging and compartment structure first, which is the subject of the next two posts.