Quick Answer
The answer is to increase the DMS replication instance class. This is the correct choice because when AWS DMS operates in Full LOB mode, it must buffer the entire LOB data in memory before writing it to the target, and a memory allocation error directly signals that the current instance lacks the RAM needed for these buffers. On the AWS Certified Database Specialty DBS-C01 exam, this scenario tests your understanding of DMS resource tuning for large objects; a common trap is to assume you should switch to Limited LOB mode or adjust task settings, but the direct fix for a memory allocation failure is scaling up the instance. Remember that Full LOB mode is memory-intensive by design, so when you see a memory error during a full LOB migration, think "bigger instance, bigger buffer." A helpful mnemonic is "LOB = Lots Of Buffering," reminding you that memory is the bottleneck.
This DBS-C01 practice question tests your understanding of deployment and migration. 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.
A company is migrating a 5 TB SQL Server database to Amazon RDS for SQL Server using AWS DMS. They are using Full LOB mode. The migration is failing with an error about memory allocation. What should they do to resolve this?
Decrease the MaxLobSize setting.
Why wrong: This switches to Limited LOB mode.
Increase the DMS replication instance class.
More memory resolves allocation errors.
Split the migration into multiple DMS tasks.
Why wrong: May reduce per-task memory but not directly.
Enable BatchApply on the DMS task.
Why wrong: BatchApply improves apply performance, not memory.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Increase the DMS replication instance class.
The error about memory allocation when using Full LOB mode in AWS DMS indicates that the replication instance does not have sufficient memory to buffer the LOB data during migration. Increasing the replication instance class provides more memory, allowing DMS to handle the LOB data without hitting allocation limits. This is the direct and recommended fix for memory-related failures in DMS LOB migrations.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Decrease the MaxLobSize setting.
Why it's wrong here
This switches to Limited LOB mode.
Increase the DMS replication instance class.
Why this is correct
More memory resolves allocation errors.
Related concept
Read the scenario before looking for a memorised answer.
Split the migration into multiple DMS tasks.
Why it's wrong here
May reduce per-task memory but not directly.
Enable BatchApply on the DMS task.
Why it's wrong here
BatchApply improves apply performance, not memory.
Common exam traps
The trap here is that candidates might confuse memory allocation errors with network or throughput issues and incorrectly choose to split the task or adjust LOB settings, rather than recognizing that the root cause is insufficient instance memory for Full LOB mode.
Detailed technical explanation
In Full LOB mode, DMS loads entire LOBs into memory before writing to the target, which can exhaust the instance's memory if LOBs are large or numerous. The replication instance's memory is shared across all DMS tasks, and the default memory allocation for LOB processing is tied to the instance class; upgrading to a larger class (e.g., from dms.c5.large to dms.c5.xlarge) increases available memory. In real-world scenarios, this error often occurs with multi-TB databases containing large BLOBs or CLOBs, where even moderate instance classes (e.g., 4 GB RAM) are insufficient.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Deployment and Migration — This question tests Deployment and Migration — Read the scenario before looking for a memorised answer..
The correct answer is: Increase the DMS replication instance class. — The error about memory allocation when using Full LOB mode in AWS DMS indicates that the replication instance does not have sufficient memory to buffer the LOB data during migration. Increasing the replication instance class provides more memory, allowing DMS to handle the LOB data without hitting allocation limits. This is the direct and recommended fix for memory-related failures in DMS LOB migrations.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This DBS-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 DBS-C01 exam.
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