- A
Use Database Migration Service (DMS) with Oracle as source and AlloyDB as destination
DMS supports Oracle (via CDC) to AlloyDB, providing full dump + continuous replication for near-zero downtime.
- B
Use Dataflow to stream Oracle changes from Pub/Sub to AlloyDB
Why wrong: Without a change capture tool (like DMS or Oracle GoldenGate), Dataflow cannot directly read Oracle redo logs.
- C
Use Ora2Pg for the full dump, then manually capture Oracle redo logs and apply them to AlloyDB
Why wrong: Manual CDC is error-prone and not recommended for production; DMS automates this.
- D
Export Oracle data to CSV, load into AlloyDB, then use a custom script with cron to apply changes
Why wrong: This is not real-time and would cause significant downtime.
Question 394 of 980
PCD Practice Question: Manage a Solution that Can Span Multiple Database Systems
This PCD practice question tests your understanding of manage a solution that can span multiple database systems. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 2 TB Oracle database to AlloyDB for PostgreSQL using Oracle to PostgreSQL migration tool (Ora2Pg). The migration must have minimal downtime. The team plans to use a two-phase approach: first a full dump, then incremental CDC. However, Ora2Pg does not natively support CDC. How should they achieve near-zero downtime migration?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"first"Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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
✓
Use Database Migration Service (DMS) with Oracle as source and AlloyDB as destination
Database Migration Service (DMS) supports continuous change data capture (CDC) from Oracle to AlloyDB for PostgreSQL, enabling near-zero downtime migration. Unlike Ora2Pg, which only handles full dump and restore, DMS uses Oracle LogMiner or binary logs to capture incremental changes and apply them to AlloyDB in near real-time, making it the correct choice for a two-phase migration with minimal downtime.
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.
- ✓
Use Database Migration Service (DMS) with Oracle as source and AlloyDB as destination
Why this is correct
DMS supports Oracle (via CDC) to AlloyDB, providing full dump + continuous replication for near-zero downtime.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use Dataflow to stream Oracle changes from Pub/Sub to AlloyDB
Why it's wrong here
Without a change capture tool (like DMS or Oracle GoldenGate), Dataflow cannot directly read Oracle redo logs.
- ✗
Use Ora2Pg for the full dump, then manually capture Oracle redo logs and apply them to AlloyDB
Why it's wrong here
Manual CDC is error-prone and not recommended for production; DMS automates this.
- ✗
Export Oracle data to CSV, load into AlloyDB, then use a custom script with cron to apply changes
Why it's wrong here
This is not real-time and would cause significant downtime.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that Ora2Pg can be extended with manual CDC scripts or that Dataflow is a simpler alternative, but the trap here is that DMS is the only Google Cloud managed service that natively supports Oracle-to-AlloyDB CDC without requiring custom development or external tools.
Detailed technical explanation
How to think about this question
DMS for Oracle to AlloyDB leverages Oracle's LogMiner to read archived redo logs and online redo logs, converting DML operations into equivalent PostgreSQL statements. It handles data type mappings (e.g., NUMBER to NUMERIC, VARCHAR2 to TEXT) and schema transformations automatically, while maintaining transaction consistency through a checkpoint-based recovery mechanism. In real-world scenarios, DMS can sustain CDC throughput of thousands of transactions per second, making it suitable for large databases like 2 TB with minimal replication 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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FAQ
Questions learners often ask
What does this PCD question test?
Manage a Solution that Can Span Multiple Database Systems — This question tests Manage a Solution that Can Span Multiple Database Systems — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use Database Migration Service (DMS) with Oracle as source and AlloyDB as destination — Database Migration Service (DMS) supports continuous change data capture (CDC) from Oracle to AlloyDB for PostgreSQL, enabling near-zero downtime migration. Unlike Ora2Pg, which only handles full dump and restore, DMS uses Oracle LogMiner or binary logs to capture incremental changes and apply them to AlloyDB in near real-time, making it the correct choice for a two-phase migration with minimal downtime.
What should I do if I get this PCD 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: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jul 4, 2026
This PCD 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 PCD exam.
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