LEARN. PRACTICE. GROW.Concept and mechanism
Azure SQL Database, Managed Instance, and SQL Server on VMs share technology but offer different contracts. SQL Database reduces instance administration and offers options including elastic pools and serverless. Managed Instance provides instance capabilities, including SQL Agent with documented limitations. A VM permits operating-system control along with patching, backup, and availability responsibilities. Selection starts with application dependencies and operational requirements. An elastic pool shares resources across databases: measure aggregate demand and peak overlap. Serverless has its own scaling and auto-pause rules and should not be confused with pooling. Partitioning organizes a table within one database; distributing data across databases requires another design. Keep the intended responsibility split explicit when estimating project effort.
Guided application
In a fictional fund project, inventory jobs, logins, integrations, volume, and windows before selecting the destination. Compression can reduce I/O while increasing CPU, so rehearsal must measure duration and throughput rather than size alone. During online migration, control data and schema changes and define the cutover write boundary. Confirm final synchronization before reopening traffic. Counts help but do not establish permissions, schedules, or functional correctness. The plan needs owners, go/no-go criteria, return time, and reconciliation. Retain one write source during transition unless an explicit design handles cross-system concurrency and conflicts. Record differences between the rehearsal workload and expected production demand.
Three databases with alternating peaks may benefit from a pool; if all peaks coincide at close, aggregate capacity is still needed.
Common pitfalls
PaaS as universal compatibility; pool as unlimited capacity; copying as completed migration.
Related topics: Identity, networking, and encryption · Sensitive data and evidence · Query Store and concurrency
Accept the target through demonstrated compatibility and operation.
Reference: Azure SQL service choices · DP-300 English objectives effective 2026-04-24