DEA-C01 Data Ingestion and Transformation Practice Question
A company uses AWS DMS to migrate an on-premises PostgreSQL database to Amazon RDS for PostgreSQL. After initial load, ongoing replication is set up. The replication task shows 'Task status: failed with error: The specified LSN is not available in the source database logs.' What is the most likely cause?
⚠ Common exam trap
Candidates often confuse connectivity issues (Option B) or general CDC support (Option A) with the specific LSN error, which is a WAL retention problem unique to PostgreSQL logical replication.
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
✓
The source database's WAL retention period is too short, and required logs have been purged.
The error 'The specified LSN is not available in the source database logs' indicates that AWS DMS is trying to read a Write-Ahead Log (WAL) position that has already been purged. PostgreSQL sources require sufficient WAL retention to allow DMS to catch up during ongoing replication (CDC). If the WAL segments are recycled or removed before DMS reads them, the replication task fails with this specific LSN error.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
DMS does not support PostgreSQL as a source for ongoing replication.
Why it's wrong here
DMS fully supports PostgreSQL as a source.
- ✗
The source database's network security group blocks outbound traffic to DMS.
Why it's wrong here
Network issues would cause connectivity errors, not LSN errors.
- ✗
The full load was incomplete, preventing CDC from starting.
Why it's wrong here
Ongoing replication can be set up after full load; if full load succeeded, this is not the issue.
- ✓
The source database's WAL retention period is too short, and required logs have been purged.
Why this is correct
DMS uses WAL logs for CDC; if logs are purged, replication fails.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.