The correct answer is to use Azure Database Migration Service with online migration. This approach is ideal because Azure DMS online mode leverages continuous change data capture (CDC) to synchronize ongoing transactions from the on-premises SQL Server to Azure SQL Managed Instance, allowing the bulk of the 500 GB data transfer to occur in the background over the 1 Gbps link while the source remains fully operational. The downtime is then reduced to a brief cutover window when you stop the source and apply the final synchronized changes. On the Microsoft Azure Solutions Architect Expert AZ-305 exam, this scenario tests your understanding of migration strategies for high-availability requirements, often contrasting online versus offline methods. A common trap is choosing a simple backup-and-restore or offline DMS approach, which would require hours of downtime for a database of this size. Remember the memory tip: “CDC cuts cutover time”—if the question emphasizes minimizing downtime, look for continuous sync, not a single bulk transfer.
AZ-305 Design data storage solutions Practice Question
This AZ-305 practice question tests your understanding of design data storage solutions. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is migrating a large on-premises SQL Server database to Azure SQL Managed Instance. They need to minimize downtime during migration. The database is 500 GB and the network link is 1 Gbps. Which migration approach should they recommend?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use Azure Database Migration Service with online migration
Option A is correct because Azure Database Migration Service (DMS) with online migration mode uses continuous change data capture (CDC) to synchronize ongoing changes from the on-premises SQL Server to Azure SQL Managed Instance, minimizing downtime to a brief cutover window. This approach is ideal for a 500 GB database over a 1 Gbps link, as it avoids the lengthy full data transfer required by offline methods.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 Database Migration Service with online migration
Why this is correct
Online migration via DMS allows continuous replication with minimal downtime, suitable for a 500 GB database.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Perform offline backup and restore
Why it's wrong here
Offline backup/restore requires the source database to be offline during backup and transfer, causing significant downtime.
✗
Use transactional replication
Why it's wrong here
Transactional replication can be complex to set up and may not provide the same level of automated synchronization as DMS online.
✗
Export BACPAC and import
Why it's wrong here
BACPAC export/import is an offline method and can be slow for large databases, causing extended downtime.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume offline backup and restore is the simplest and fastest method, but they overlook the 'minimize downtime' requirement, which makes online migration via DMS the only correct choice despite its added complexity.
Detailed technical explanation
How to think about this question
Azure DMS online migration leverages the Log Reader Agent to capture transaction log changes from the source SQL Server and apply them continuously to the target Managed Instance, using a full backup as the initial baseline. The 1 Gbps link is sufficient for the initial data transfer and ongoing log shipping, but network latency and throughput must be monitored to avoid log growth issues. In real-world scenarios, if the source database has high transaction rates, DMS may fall behind, requiring a larger network pipe or throttling writes during cutover.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-305 question in full detail.
Design data storage solutions — This question tests Design data storage solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use Azure Database Migration Service with online migration — Option A is correct because Azure Database Migration Service (DMS) with online migration mode uses continuous change data capture (CDC) to synchronize ongoing changes from the on-premises SQL Server to Azure SQL Managed Instance, minimizing downtime to a brief cutover window. This approach is ideal for a 500 GB database over a 1 Gbps link, as it avoids the lengthy full data transfer required by offline methods.
What should I do if I get this AZ-305 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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