- A
Reduce the batch size for the CDC phase.
Why wrong: Not a configurable parameter in DMS.
- B
Increase the source database's resources (CPU/memory) to handle logical replication load.
The source may be under-resourced to publish changes fast enough.
- C
Increase the number of DMS worker nodes.
Why wrong: DMS worker nodes are auto-scaled; not directly configurable.
- D
Add more indexes to the target AlloyDB tables.
Why wrong: Indexes slow down writes, making lag worse.
Question 743 of 1,000
PCDOE Migrate Database Solutions Practice Question
This PCDOE practice question tests your understanding of migrate database solutions. 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 team is migrating a 10 TB PostgreSQL database to AlloyDB using DMS with continuous CDC. The migration starts, but the CDC phase is falling behind, with lag increasing over time. The source is a busy production database with high write throughput. What is the most effective action to reduce lag?
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
✓
Increase the source database's resources (CPU/memory) to handle logical replication load.
Option B is correct because increasing the source database's resources (CPU/memory) directly addresses the root cause of CDC lag in a high-write-throughput PostgreSQL environment. DMS logical replication relies on the source's ability to decode WAL (Write-Ahead Log) records quickly; if the source is CPU- or memory-bound, it cannot keep up with the rate of changes, causing lag to grow. Scaling up the source reduces the bottleneck in WAL generation and decoding, allowing DMS to consume changes faster.
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.
- ✗
Reduce the batch size for the CDC phase.
Why it's wrong here
Not a configurable parameter in DMS.
- ✓
Increase the source database's resources (CPU/memory) to handle logical replication load.
Why this is correct
The source may be under-resourced to publish changes fast enough.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Increase the number of DMS worker nodes.
Why it's wrong here
DMS worker nodes are auto-scaled; not directly configurable.
- ✗
Add more indexes to the target AlloyDB tables.
Why it's wrong here
Indexes slow down writes, making lag worse.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that scaling DMS workers (Option C) always fixes CDC lag, but the trap is that the bottleneck in high-write environments is typically the source's ability to decode WAL, not DMS's processing capacity.
Detailed technical explanation
How to think about this question
PostgreSQL logical replication uses a replication slot to stream WAL changes; the slot's 'restart_lsn' advances only after the consumer (DMS) acknowledges receipt. If the source is under-provisioned, WAL generation outpaces decoding, causing the slot to hold back cleanup and potentially leading to disk-full scenarios. In real-world migrations, monitoring pg_stat_replication and pg_replication_slots for 'write_lag' and 'flush_lag' helps pinpoint whether the bottleneck is source-side (high write_lag) or network/apply-side (high flush_lag).
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.
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Migrate Database Solutions — study guide chapter
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FAQ
Questions learners often ask
What does this PCDOE question test?
Migrate Database Solutions — This question tests Migrate Database Solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Increase the source database's resources (CPU/memory) to handle logical replication load. — Option B is correct because increasing the source database's resources (CPU/memory) directly addresses the root cause of CDC lag in a high-write-throughput PostgreSQL environment. DMS logical replication relies on the source's ability to decode WAL (Write-Ahead Log) records quickly; if the source is CPU- or memory-bound, it cannot keep up with the rate of changes, causing lag to grow. Scaling up the source reduces the bottleneck in WAL generation and decoding, allowing DMS to consume changes faster.
What should I do if I get this PCDOE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
This PCDOE practice question is part of Courseiva's free Google Cloud 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 PCDOE exam.
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