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Difficulty: MediumDesigning Migration Plans and Data Transfer Strategies

An enterprise pharmaceutical firm is migrating an on-premises Oracle relational database and historical clinical trial data archives to Google Cloud. The target architecture uses Cloud SQL for PostgreSQL for operational data and Cloud Storage for unstructured archives. To ensure minimal downtime and data integrity during cutover, place the migration workflow steps in the correct chronological order from first to last.

  1. 1Establish Dedicated Interconnect hybrid networking and configure firewall rules between the on-premises data center and Google Cloud VPC.
  2. 2Execute historical archive transfer via Storage Transfer Service and start continuous change data capture (CDC) replication via Database Migration Service (DMS).
  3. 3Stop incoming write traffic on the on-premises source database and confirm that DMS replication lag drops to zero.
  4. 4Promote the Cloud SQL target instance to a standalone database and redirect application connection strings to the new endpoint.

Answer

The correct chronological sequence for a minimal-downtime database and archive migration is: 1) Establish Dedicated Interconnect hybrid networking, 2) Execute historical transfer via Storage Transfer Service and configure CDC replication via Database Migration Service, 3) Stop incoming write traffic on-premises and wait for replication lag to reach zero, 4) Promote the Cloud SQL target instance and update application connection strings.
The correct order follows standard Google Cloud architecture migration staging patterns: first establishing private hybrid connectivity (Dedicated Interconnect), then running bulk file transfers alongside continuous CDC replication via Database Migration Service, followed by stopping source write traffic to drain remaining replication lag to zero, and finally promoting the destination database while pointing application workloads to the new endpoint.

Step-by-Step Solution

1
Establish hybrid connectivity and network security controls.
On-premises environment securely communicates with the Google Cloud VPC via Dedicated Interconnect.
Data transfer tools require secure, high-bandwidth private network paths before executing data movement.
2
Initiate bulk archival data transfer and start continuous CDC database replication.
Historical files land in Cloud Storage while ongoing transactional changes stream continuously into Cloud SQL.
Combining bulk loading with continuous replication establishes a baseline without disrupting live production traffic.
3
Quiesce the source database and verify zero replication lag.
No new transactions occur on-premises, and all pending changes apply to the target Cloud SQL database.
Pausing writes ensures transaction consistency and prevents split-brain conditions during final cutover.
4
Promote the Cloud SQL instance and switch application configuration endpoints.
Applications resume normal operation pointing directly to Google Cloud infrastructure.
Promoting the database detaches CDC replication and establishes Cloud SQL as the primary operational system.

Key Concept

Staged Migration Workflow and Database Cutover Strategy
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Topics

Designing Migration Plans and Data Transfer Strategies