If you do have usage tracking configured and enabled, query the usage tracking table and you will be able to get a list.

By default the table is S_NQ_ACCT in the BIPLATFORM schema, but you maybe configured a different table somewhere else.

You can verify if usage tracking is on (the people installing that OAS hopefully did enable it, not many reasons to not do it) by looking in DV > Console > System Settings > Usage Tracking. You will also find the details of the database table used to store the information. You can find details about the table and the meaning of columns in https://docs.oracle.com/en/middleware/bi/analytics-server/administer-oas/understand-usage-tracking-tables.html , as well as 2 possible ways to do that analysis: dataset or exposing it via the semantic model.

If you don't have usage tracking, you could start parsing log files. But logs are rotated and you could maybe not have the required data anymore.