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This question is part of a case study — click to read the full scenario(Case 06)

CASE STUDY: RetailMart

Overview: Global e-commerce, 5,000 employees. Legacy monolith on VMware, 20TB Oracle DB on-prem.
Business: Modernize to microservices, 100% uptime during Black Friday (10x traffic), real-time inventory sync, exit data center in 2 years.
Executives:

  • CEO: "Innovate faster to beat online-only competitors."
  • CFO: "End hardware CAPEX. Move to pure OPEX."
  • CTO: "Break monolith safely. Zero downtime during transition."
    Tech: Migrate off Oracle to open-source, containerize, secure hybrid connectivity during transition, automated scaling.
    Constraints: Zero downtime for storefront, heavy reliance on Oracle stored procedures, all hybrid traffic must be private/encrypted.

Which migration approach should you recommend to safely break down the monolith with zero downtime?

GCP PCA · Question 08 · Domain 1: Designing and Planning a Cloud Solution Architecture

CASE STUDY: RetailMart

Overview: Global e-commerce, 5,000 employees. Legacy monolith on VMware, 20TB Oracle DB on-prem.
Business: Modernize to microservices, 100% uptime during Black Friday (10x traffic), real-time inventory sync, exit data center in 2 years.
Executives:

  • CEO: "Innovate faster to beat online-only competitors."
  • CFO: "End hardware CAPEX. Move to pure OPEX."
  • CTO: "Break monolith safely. Zero downtime during transition."
    Tech: Migrate off Oracle to open-source, containerize, secure hybrid connectivity during transition, automated scaling.
    Constraints: Zero downtime for storefront, heavy reliance on Oracle stored procedures, all hybrid traffic must be private/encrypted.

Which strategy should you use to migrate the 20TB Oracle database to an open-source solution with zero downtime?

Answer options:

A.

Export the Oracle database to CSV files, upload to Cloud Storage, and import into Cloud Spanner.

B.

Use Datastream to replicate data continuously from Oracle to Cloud SQL for PostgreSQL, and rewrite the stored procedures in the application layer.

C.

Migrate to Bare Metal Solution for Oracle to maintain the stored procedures.

D.

Use Database Migration Service (DMS) to migrate directly to BigQuery.

How to approach this question

Look for a continuous replication tool (CDC) to ensure zero downtime, and ensure the target is open-source.

Full Answer

B.Use Datastream to replicate data continuously from Oracle to Cloud SQL for PostgreSQL, and rewrite the stored procedures in the application layer.✓ Correct
Use Datastream to replicate data continuously from Oracle to Cloud SQL for PostgreSQL, and rewrite the stored procedures in the application layer.
To achieve zero downtime, you must use Change Data Capture (CDC) to keep the target database in sync with the source until cutover. Google Cloud Datastream supports Oracle as a source and Cloud SQL for PostgreSQL as a destination. Because the legacy app relies heavily on Oracle stored procedures, this business logic must be refactored, ideally into the new microservices application layer.

Common mistakes

Choosing Bare Metal Solution (C) - while this is the easiest way to keep Oracle, it directly contradicts the requirement to move to open-source.

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