DEA-C01 Data Operations and Support Practice Question
A data engineer is troubleshooting an AWS Glue ETL job that suddenly started failing with 'An error occurred while calling o103.pyWriteDynamicFrame. Unknown error'. The job writes data to an Amazon Redshift table. Which step should the engineer take FIRST?
⚠ Common exam trap
DEA-C01 often tests the principle of 'logs first' in troubleshooting scenarios, where candidates are tempted to jump to speculative fixes like changing configurations or drivers instead of gathering diagnostic data.
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
✓
Review the job's CloudWatch Logs for detailed error messages.
The error message 'An error occurred while calling o103.pyWriteDynamicFrame. Unknown error' is a generic wrapper thrown by the Glue DynamicFrame writer when the underlying cause is not surfaced. The first and most reliable step is to inspect the job's CloudWatch Logs, where the full stack trace, Redshift error code, and driver-level messages are recorded. This aligns with standard AWS troubleshooting guidance: always check logs before making changes. Reviewing logs is non-destructive, fast, and directly reveals the root cause (e.g., permission issue, connection timeout, schema mismatch).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Recreate the Redshift table with a different distribution style.
Why it's wrong here
Recreating the table with a different distribution style is not the first step; distribution affects query performance, not a sudden write failure. It is tempting because skew causes load problems, and would be correct when diagnosing slow COPY operations rather than an immediate unknown write error.
- ✗
Test the job with a small sample dataset to isolate the issue.
Why it's wrong here
Sampling data tests the transformation logic, not the Redshift write path where pyWriteDynamicFrame fails. The error surfaces during the write, so the engineer should inspect the Redshift connection, staging bucket permissions and cluster state first. Small-sample testing suits validating schema or logic changes before full runs.
- ✗
Update the Redshift JDBC driver version in the Glue job.
Why it's wrong here
Updating the JDBC driver is not the first step; the job previously succeeded, so a driver change would not explain a sudden failure. It is tempting because driver incompatibility causes write errors, and would be correct after confirming the Redshift cluster, credentials and schema are unchanged.
- ✓
Review the job's CloudWatch Logs for detailed error messages.
Why this is correct
The error message 'An error occurred while calling o103.pyWriteDynamicFrame. Unknown error' is generic and does not specify the root cause. The first troubleshooting step should be to review the job's CloudWatch Logs, which provide detailed error messages, stack traces, and other diagnostic information.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Amazon Web Services exam blueprint
This DEA-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DEA-C01 exam.