The answer is that the source SQL Server transaction log has not been backed up or truncated, causing it to become full. This is correct because AWS DMS relies on reading the source database’s transaction log to capture ongoing changes during Change Data Capture (CDC) replication; when the log is full and cannot accept new entries, DMS cannot read the log records needed for continuous synchronization. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of DMS CDC prerequisites and common operational pitfalls—specifically that a full transaction log is a frequent cause of replication failure, often mistaken for a network or permissions issue. A common trap is assuming the error points to disk space on the DMS instance rather than the source database’s log management. Memory tip: “A full log stops the log—back up to keep CDC on track.”
SAP-C02 Practice Question: Accelerate Workload Migration and Modernization
This SAP-C02 practice question tests your understanding of accelerate workload migration and modernization. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Exhibit
Refer to the exhibit.
Error log from AWS DMS task:
"Last Error 1201: Could not start capture. The SQL Server log file 'LDF' is full. Stop the capture and free up space in the log file."
Task details:
- Source: SQL Server on EC2 (Full CDC mode)
- Target: Amazon Redshift
- DMS task type: Migrate existing data and replicate ongoing changes
- Task status: Failed with error after initial load completed successfully
A company is using AWS DMS to migrate a SQL Server database to Amazon Redshift. The initial full load completed, but the ongoing replication task failed with the error shown. What is the MOST likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Refer to the exhibit.
Error log from AWS DMS task:
"Last Error 1201: Could not start capture. The SQL Server log file 'LDF' is full. Stop the capture and free up space in the log file."
Task details:
- Source: SQL Server on EC2 (Full CDC mode)
- Target: Amazon Redshift
- DMS task type: Migrate existing data and replicate ongoing changes
- Task status: Failed with error after initial load completed successfully
A
The DMS task is not configured to use a task log for troubleshooting.
Why wrong: Task log configuration does not cause source log file errors.
B
The source SQL Server transaction log has not been backed up or truncated, causing it to become full.
CDC reads the transaction log; if it fills up, DMS cannot continue. Regular log backups or truncation are needed.
C
The target Redshift table does not have a primary key defined for the DMS task to apply changes.
Why wrong: Primary key is needed for CDC tasks, but missing primary key would cause a different error, not a log file full error.
D
The DMS task is using a full LOB mode, which is not supported for Redshift targets.
Why wrong: Full LOB mode is supported for Redshift; this would not cause a source log file full error.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The source SQL Server transaction log has not been backed up or truncated, causing it to become full.
The error indicates that AWS DMS cannot read the source SQL Server transaction log to capture ongoing changes. This typically occurs when the transaction log is full because it has not been backed up or truncated, preventing DMS from reading new log records for continuous replication. DMS relies on the source database's transaction log for CDC (Change Data Capture), and a full log blocks this process.
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.
✗
The DMS task is not configured to use a task log for troubleshooting.
Why it's wrong here
Task log configuration does not cause source log file errors.
✓
The source SQL Server transaction log has not been backed up or truncated, causing it to become full.
Why this is correct
CDC reads the transaction log; if it fills up, DMS cannot continue. Regular log backups or truncation are needed.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The target Redshift table does not have a primary key defined for the DMS task to apply changes.
Why it's wrong here
Primary key is needed for CDC tasks, but missing primary key would cause a different error, not a log file full error.
✗
The DMS task is using a full LOB mode, which is not supported for Redshift targets.
Why it's wrong here
Full LOB mode is supported for Redshift; this would not cause a source log file full error.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse a target-side issue (like missing primary key or unsupported LOB mode) with a source-side transaction log problem, because the error message explicitly mentions 'transaction log' but test-takers often overlook the source database context.
Detailed technical explanation
How to think about this question
AWS DMS for SQL Server CDC uses the native SQL Server transaction log reader (similar to log reader agent) to capture INSERT, UPDATE, and DELETE operations. If the transaction log becomes full (e.g., due to a long-running transaction or lack of log backups), DMS cannot read new log records, causing the task to fail with a 'cannot read transaction log' error. In production, this is often mitigated by setting up regular transaction log backups (e.g., every 5-15 minutes) to keep the log from growing unbounded and to allow DMS to advance its log sequence number (LSN) tracking.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Accelerate Workload Migration and Modernization — This question tests Accelerate Workload Migration and Modernization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The source SQL Server transaction log has not been backed up or truncated, causing it to become full. — The error indicates that AWS DMS cannot read the source SQL Server transaction log to capture ongoing changes. This typically occurs when the transaction log is full because it has not been backed up or truncated, preventing DMS from reading new log records for continuous replication. DMS relies on the source database's transaction log for CDC (Change Data Capture), and a full log blocks this process.
What should I do if I get this SAP-C02 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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is migrating a 5 TB Microsoft SQL Server database to Amazon RDS for SQL Server. The migration must have minimal downtime. The team uses AWS DMS with ongoing replication. During the full load, the task fails with an error indicating that the source server's transaction log is full. What should the team do to resolve this issue?
hard
A.Stop the DMS task, take a native backup of the source, restore it to RDS, and then start DMS with ongoing replication.
✓ B.Increase the source server's transaction log size and set the log retention to a higher value.
C.Pause the DMS task, create a larger source instance, and restart the task.
D.Switch the DMS task to use batch-optimized apply mode.
Why B: Option B is correct because the error indicates the source transaction log is full during the full load phase of AWS DMS. Increasing the transaction log size and setting a higher log retention value prevents the log from filling up while DMS reads it for ongoing replication. This allows the full load to complete without interruption, addressing the root cause directly.
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Question Discussion
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