Question 826 of 1,446
Oracle to Cloud SQL Migration: Key Prerequisites
A company is planning to migrate their on-premises Oracle database to Cloud SQL. Which THREE prerequisites must be satisfied?
Quick Answer
The answer is that setting up VPC peering or a VPN to connect on-premises to Google Cloud is one of three key prerequisites for migrating Oracle to Cloud SQL. This is correct because Cloud SQL does not support Oracle’s proprietary PL/SQL syntax, meaning you must convert Oracle-specific elements like sequences, packages, and hierarchical queries to the target dialect—either PostgreSQL or MySQL—before migration. On the Google Professional Cloud Database Engineer exam, this question tests your understanding that network connectivity and syntax conversion are foundational steps, not optional optimizations. A common trap is assuming Cloud SQL can natively run Oracle code, but the exam emphasizes that only PostgreSQL and MySQL engines are available. For a memory tip, think “Connect and Convert”: first establish the network link via VPC or VPN, then convert PL/SQL to the target dialect to ensure the database functions correctly post-migration.
⚠ Common exam trap
Google Cloud often tests the misconception that Cloud SQL supports Oracle as a native engine, leading candidates to overlook the mandatory syntax conversion, or that a staging bucket is always required when DMS can perform direct migration without intermediate storage.
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
✓
Convert Oracle-specific syntax to PostgreSQL or MySQL
Cloud SQL does not support Oracle's proprietary PL/SQL syntax. When migrating from Oracle to Cloud SQL, you must convert Oracle-specific syntax (e.g., sequences, packages, hierarchical queries) to the target dialect—either PostgreSQL or MySQL—since Cloud SQL offers only these two engines. This conversion is a prerequisite to ensure the migrated database functions correctly after the move.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Convert Oracle-specific syntax to PostgreSQL or MySQL
Why this is correct
Database Migration Service handles schema conversion, but manual tuning may be needed.
- ✗
Purchase Cloud SQL Enterprise Plus edition for the target instance
Why it's wrong here
Enterprise Plus is not required for migration; any edition works.
- ✓
Ensure the source database is compatible with Database Migration Service (DMS)
Why this is correct
DMS supports specific source versions and configurations.
- ✓
Set up VPC peering or VPN to connect on-premises to Google Cloud
Why this is correct
Network connectivity is required for replication.
- ✗
Create a Cloud Storage bucket for staging migration data
Why it's wrong here
A staging bucket is optional and not a prerequisite; DMS can stream directly.
Visual reference
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Same concept, more angles
2 more ways this is tested on PCDE
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is migrating an on-premises Oracle database to Cloud SQL for PostgreSQL. The database is 2 TB in size and the network bandwidth to Google Cloud is limited to 500 Mbps. The migration window is 48 hours. Which migration strategy should the Database Engineer recommend?
medium- A.Create a VPN tunnel and use pg_dump/pg_restore over the network.
- B.Use Database Migration Service with continuous replication.
- ✓ C.Export the database to flat files, compress, upload to Cloud Storage, then import to Cloud SQL.
- D.Request a dedicated interconnect and then migrate.
Why C: The 2 TB database size and 500 Mbps bandwidth yield a theoretical transfer time of approximately 9.5 hours (2 TB * 1024 GB/TB * 8 bits/byte / 500 Mbps / 3600 seconds/hour), which fits within the 48-hour window. However, pg_dump/pg_restore over a VPN (Option A) would be slower due to TCP overhead and latency, and Database Migration Service with continuous replication (Option B) requires ongoing connectivity and may not complete the initial load within the window. Exporting to flat files, compressing them (e.g., with gzip), uploading to Cloud Storage, and then importing to Cloud SQL leverages high-throughput parallel uploads and avoids network latency issues, making it the most reliable strategy for a one-time migration within the given constraints.
Variation 2. A company is migrating their on-premises Oracle database to Cloud SQL for PostgreSQL. They want to minimize downtime during the cutover. Which two strategies should the database engineer recommend? (Choose 2.)
medium- A.Use a Cloud VPN tunnel for data transfer.
- ✓ B.Use Database Migration Service with continuous replication.
- C.Use a third-party tool like pglogical for replication.
- D.Use Cloud SQL for PostgreSQL with read replicas and promote.
- E.Perform an export using pg_dump and import using psql.
Why B: Database Migration Service (DMS) with continuous replication is the only strategy that enables minimal downtime migration from Oracle to Cloud SQL for PostgreSQL. DMS handles full data load and ongoing change replication until cutover. Option C (pglogical) is invalid because pglogical only supports replication between PostgreSQL databases, not from Oracle. Option D (read replicas and promote) is not a migration strategy from an external Oracle database; it is for scaling within PostgreSQL. Options A and E involve significant downtime.
Last reviewed: Jun 30, 2026
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