This blog post discusses high-availability (HA) architecture for mission-critical Oracle databases on Microsoft Azure, specifically using FlashGrid Cluster to enable Oracle RAC across availability zones. Organizations face choices between Oracle AI Database@Azure, self-managed single instances, or Oracle RAC. Oracle Data Guard helps protect against availability zone failures by maintaining a standby database.Oracle RAC offers active-active HA with zero downtime during rolling maintenance and near-zero recovery time objectives (RTO) during unexpected failures, outperforming Data Guard for mission-critical HA. Azure recommends multi-VM deployments across availability zones for 99.99% uptime SLA. Two multi-AZ options for Oracle RAC are proposed: two RAC clusters with Data Guard replication or one RAC cluster spanning two or three availability zones.Option A, two RAC clusters with Data Guard, duplicates resources, increasing cost and operational complexity. It also introduces Data Guard failover time, impacting the uptime SLA. Option B, a single multi-AZ RAC cluster, offers the same HA capabilities as a local RAC cluster, plus protection against availability zone failures. FlashGrid Cluster simplifies this complex deployment with automated Azure Resource Manager templates and pre-tested components.Deployment takes only 30-90 minutes, making it faster and simpler than typical on-premises Oracle RAC deployments. Network latency between Azure availability zones is typically less than 1ms, not critically impacting most workloads. For latency-sensitive Cache Fusion operations, a preferred database instance can minimize cross-node traffic.Neither option provides a complete disaster recovery solution; a multi-region DR strategy is needed for regional outages, typically using asynchronous Data Guard or Oracle GoldenGate. FlashGrid Cluster automates the infrastructure for multi-AZ Oracle RAC on Azure, offering rapid recovery, rolling maintenance support, and protection against availability zone failures without duplicating clusters or relying on Data Guard FSFO. FlashGrid Cluster is available on the Microsoft Marketplace, with production deployments since 2017.