One of the query that is using multiple additionable views is performing poorly with optimizer 12.1.0.2. After changing optimizer feature to 11.2.0.4 query is running fine and taking NL in place of Hash join. We don't have option to change query and exploring opportunities to enforce query plan by using query baseline or plan management. But before that to fix it immediately, want to downgrade optimizer_feature_enabled to 11.2.0.4.
Please advice will it have any negative impact on oracle functionality. As per my understanding it's just optimizer change so functionality will remain intact and it will not have any functional impact on other processes.