Over the last 12 months, Operations Management Suite (OMS) monitoring, management and security capabilities have been incorporated into the Azure portal. We have also enhanced the Azure portal with many new features and capabilities.
Because the Azure portal fully replaces it, the OMS portal will be retired on 15th January 2019. You can continue to use your existing services and licensing in the Azure portal.
You can read more about the move from the OMS portal to the Azure portal in the documentation. If you have any questions or concerns, reach out to us at LAUpgradeFeedback@microsoft.com.