A company has an on-premises SQL Server database with a 1 TB 'Sales' table containing historical data. They want to move this table to Azure SQL Database with minimal downtime. The table is actively written to during business hours. Which approach should they use?
Azure Database Migration Service with continuous sync is the correct online method because it reads the source transaction log and continuously applies those changes to the target Azure SQL Database, all while the on-premises database remains online and fully operational. The migration can run for days to sync historical data without blocking active workloads, and only the final cutover step—stopping the source and pointing the application to the target—requires a brief downtime window measured in minutes. Unlike offline approaches, this preserves continuity for a 1 TB database and provides validation and rollback capability during the migration.
Why this answer
Azure Data Migration Service (DMS) with continuous sync is the correct approach because it supports online migration with minimal downtime. It uses transactional replication to keep the on-premises SQL Server database synchronized with Azure SQL Database while the source remains fully operational, allowing a controlled cutover with only seconds of downtime.
Exam trap
The trap here is that candidates often assume offline methods (bacpac, wizard) are sufficient for large tables, underestimating the downtime required for a 1 TB dataset, and fail to recognize that 'minimal downtime' explicitly requires an online migration with continuous sync.
Why the other options are wrong
This option is wrong because the question requires minimal downtime, and an offline migration over the weekend still involves downtime during the migration window. The table is actively written to during business hours, so even weekend migration may not be acceptable if the business operates beyond weekdays or requires near-zero downtime.
Exporting a 1 TB table as a .bacpac and importing it is an offline operation that requires the table to be idle, but the table is actively written to during business hours, causing data inconsistency and unacceptable downtime.
The 'Deploy Database to Azure SQL Database' wizard in SSMS performs an offline migration, which would cause significant downtime for the actively written Sales table. It does not support continuous sync to minimize downtime.