Option C provides the lowest-change migration path for the application tier. Rehosting the existing Windows workload on Windows Server ECS instances preserves its operating-system environment while distributing instances across availability zones improves resilience against zone-level infrastructure failures.
For the database tier, Option A provides the stronger managed architecture. Alibaba Cloud explicitly supports using DTS to migrate self-managed Oracle databases to PolarDB for PostgreSQL (Compatible with Oracle), including schema, full-data, and incremental-data migration for minimal migration downtime.
PolarDB ' s Oracle-compatible edition is specifically engineered to run Oracle workloads with minimal application modification. It supports Oracle-compatible data types, SQL constructs, PL/SQL features, OCI connectivity, packages, sequences, synonyms, and related functionality.
It also provides built-in high availability: failures are detected automatically and workloads can fail over to healthy nodes. This provides a more complete managed availability architecture than simply deploying independent self-managed Oracle servers across zones, which would additionally require Oracle-level replication/failover configuration.
Options B and D require substantial application refactoring and therefore conflict with the explicit requirement to minimize development changes.
Study Guide reference: Building Highly Available, Performant Cloud Architecture — workload migration, ECS multi-zone design, DTS, and PolarDB Oracle compatibility.
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