Unlike other supported DBs (mysql, postgres, mssql, memory) oracle throws errors during AO development when trying to migrate objects. I believe its related to JRA-29155 in which GH encountered it for installs, but the underlying issue is in AO.
This is particularly an issue for developers whom follow this guide - https://developer.atlassian.com/docs/atlassian-platform-common-components/active-objects/developing-your-plugin-with-active-objects/the-active-objects-library/testing
Specifying a DatabaseUpdater through the @Data annotation. It is implemented here as a static inner class (AoBlogServiceTestDatabaseUpdater). Its update method allows you to prepare the database for tests. It is called only once per class (or per set of classes with the same DatabaseUpdater).
If using the DatabaseUpdater class for your test suites, add a method that explicitly drops sequences. Hope it spares someone the hours i wasted trying to get oracle to play nice like all the other DBs.
This should be run just prior to any migrate tasks in DatabaseUpdater update() method.