DP-900 Practice Question: Identify considerations for relational data on Azure
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?
⚠ Common exam trap
Many candidates 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.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use Azure Data Migration Service with continuous sync from on-premises to Azure SQL Database, then cut over
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.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use Azure Data Migration Service with continuous sync from on-premises to Azure SQL Database, then cut over
Why this is correct
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.
- ✗
Use the Azure SQL Database migration wizard to perform an offline migration over the weekend
Why it's wrong here
The Azure SQL Database migration wizard in offline mode uses a full database backup and restore to move data, which inherently requires the source database to be taken offline or set to read-only to ensure the backup is transactionally consistent. Even if you run it over the weekend, you still force a complete outage for the duration of the backup, transfer, and restore—and for 1 TB, that duration can easily span a day or more, breaking the weekend window. Offline migration does not use log replication, so it cannot deliver the minimal-cutover guarantee that an online DMS migration provides.
When this WOULD be correct
This option would be correct if the question specified that the migration can be performed during a scheduled maintenance window where downtime is acceptable, and the table is not actively used during that time. For example: 'A company needs to migrate a 1 TB Sales table to Azure SQL Database and can schedule a 48-hour maintenance window over the weekend with no business impact.'
- ✗
Export the table as a .bacpac file and import it into Azure SQL Database during off-hours
Why it's wrong here
Exporting a .bacpac file creates a point-in-time logical snapshot of the schema and data, but it does not capture any transaction log activity that occurs after the export begins. To guarantee a consistent .bacpac, you must stop writes or put the database in read-only mode, which introduces downtime regardless of whether you schedule it during off-hours. Furthermore, for a 1 TB table, the export and import process is slow and resource-intensive, and because it is not resumable, any failure forces you to restart completely—making it a poor fit for a large, busy database.
When this WOULD be correct
A company needs to migrate a small, static database (e.g., < 20 GB) that is not being modified during migration, and they can afford several hours of downtime. The .bacpac export/import is simple and requires no additional services.
- ✗
Use SQL Server Management Studio's 'Deploy Database to Azure SQL Database' wizard
Why it's wrong here
The SSMS 'Deploy Database to Azure SQL Database' wizard is simply a graphical wrapper around a .bacpac export and import, so it shares the same fundamental limitation: it produces a static snapshot and cannot replicate ongoing changes. This means any new transactions that occur while the wizard is running—which may be many hours for 1 TB of data—will be missing from the target, causing data loss and inconsistency. It is an offline migration intended for small- to medium-sized databases, not a 1 TB production workload that demands near-zero downtime.
When this WOULD be correct
This option would be correct for a small, static database (e.g., < 50 GB) that can tolerate several hours of downtime, and when the goal is a simple one-time migration without ongoing replication.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The DP-900 exam frequently reuses these exact scenarios with slightly different constraints.
✓Use Azure Data Migration Service with continuous sync from on-premises to Azure SQL Database, then cut overCorrect answer▾
Why this is correct
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.
✗Use the Azure SQL Database migration wizard to perform an offline migration over the weekendWrong answer — click to see why▾
Why this is wrong here
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.
★ When this WOULD be the correct answer
This option would be correct if the question specified that the migration can be performed during a scheduled maintenance window where downtime is acceptable, and the table is not actively used during that time. For example: 'A company needs to migrate a 1 TB Sales table to Azure SQL Database and can schedule a 48-hour maintenance window over the weekend with no business impact.'
Why candidates choose this
Candidates may think that performing the migration over the weekend minimizes business impact and is simpler than setting up continuous sync. They might underestimate the requirement for minimal downtime or assume that weekend downtime is acceptable.
✗Export the table as a .bacpac file and import it into Azure SQL Database during off-hoursWrong answer — click to see why▾
Why this is wrong here
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.
★ When this WOULD be the correct answer
A company needs to migrate a small, static database (e.g., < 20 GB) that is not being modified during migration, and they can afford several hours of downtime. The .bacpac export/import is simple and requires no additional services.
Why candidates choose this
Candidates may think .bacpac is the standard Azure SQL migration tool and overlook the size and active-write constraints, assuming off-hours migration is sufficient.
✗Use SQL Server Management Studio's 'Deploy Database to Azure SQL Database' wizardWrong answer — click to see why▾
Why this is wrong here
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.
★ When this WOULD be the correct answer
This option would be correct for a small, static database (e.g., < 50 GB) that can tolerate several hours of downtime, and when the goal is a simple one-time migration without ongoing replication.
Why candidates choose this
Candidates may be familiar with SSMS and assume its built-in wizard is sufficient for any migration, overlooking the need for minimal downtime and continuous sync for large, active tables.
Analysis generated from the official DP-900blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Related to this question
Learn chapter
Data Roles and Core Concepts
Key term
Table
A table is a structured collection of data organized into rows and columns, used in databases and spreadsheets to store and manage information efficiently.
Key term
Data
Data is raw, unprocessed information, like numbers, words, or measurements, that can be stored, processed, and analyzed by computers.
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