Question 1,073 of 1,446
PCDE Migrate data solutions Practice Question
A company is migrating a MySQL database to Cloud SQL using Database Migration Service (DMS). The source database is on-premises and uses InnoDB tables. The migration job is configured as continuous (CDC). After starting the job, the full dump phase completes successfully, but the CDC phase shows no replicated changes. What is the most likely cause?
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
✓
The source database does not have binary logging enabled.
Continuous CDC replication in DMS requires binary logging to be enabled on the source database. If binary logging is disabled, DMS cannot capture change data. The full dump works because it uses mysqldump, which does not rely on binary logs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The Cloud SQL destination does not have public IP connectivity.
Why it's wrong here
Connectivity affects the initial connection, not the CDC phase after dump completion.
- ✗
The source database is using MyISAM tables instead of InnoDB.
Why it's wrong here
MyISAM tables can still be migrated; but the scenario specifies InnoDB. MyISAM would not prevent CDC if binary logging is enabled.
- ✗
The DMS migration job was configured as one-time instead of continuous.
Why it's wrong here
If it were one-time, there would be no CDC phase; but the scenario says CDC phase exists but shows no changes.
- ✓
The source database does not have binary logging enabled.
Why this is correct
Correct. DMS CDC requires binary logging on the source to capture ongoing changes.
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Same concept, more angles
5 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 team is migrating an on-premises PostgreSQL database to Cloud SQL using DMS. They want the migration job to continuously replicate changes after the initial dump. Which type of migration job should they create?
easy- A.One-time migration job
- B.Scheduled export job
- C.Bulk load job
- ✓ D.Continuous migration job
Why D: DMS offers 'one-time' for single dump and 'continuous' for ongoing CDC. Continuous jobs replicate changes after dump.
Variation 2. A team is migrating a 5 TB MySQL database to Cloud SQL using DMS. The full dump phase is taking longer than expected. They suspect network bandwidth is the bottleneck. Which action can they take to improve the dump speed within DMS?
hard- A.Use a larger machine type for the source connection profile.
- ✓ B.Enable parallel dump in the DMS migration job settings.
- C.Increase the Cloud SQL instance storage size.
- D.Switch to a one-time migration job instead of continuous.
Why B: DMS uses a single-threaded dump by default. Enabling parallel dump can improve speed for large databases.
Variation 3. A company is migrating a PostgreSQL database to Cloud SQL using DMS continuous migration. After the full dump, the CDC phase is replicating changes. To prepare for cutover, which TWO actions should the engineer take? (Choose 2)
medium- ✓ A.Verify that the DMS migration job lag is 0 seconds.
- B.Enable binary logging on the source.
- C.Take a full backup of the source.
- D.Delete the DMS migration job to stop replication.
- ✓ E.Quiesce all write operations to the source database.
Why A: Quiesce writes to ensure no new changes, and confirm DMS lag is 0 before promoting.
Variation 4. A team is migrating a PostgreSQL database to AlloyDB using Database Migration Service. They need to perform an initial one-time full dump without continuous replication. Which migration job type should they choose?
easy- A.Bulk
- B.Continuous
- C.Snapshot
- ✓ D.One-time
Why D: Database Migration Service supports two job types: 'One-time' (full dump only) and 'Continuous' (full dump + CDC). For a one-time migration without ongoing replication, select 'One-time'. Continuous includes CDC for ongoing sync.
Variation 5. A team is migrating a 2 TB MySQL database from on-premises to Cloud SQL. They want to minimize downtime. The source is MySQL 8.0 with InnoDB tables, and the application can be read-only during cutover. Which approach provides the lowest downtime while ensuring data consistency?
medium- A.Use mysqldump with --single-transaction to export, then import to Cloud SQL using mysql client.
- B.Use Cloud Dataflow to stream data from MySQL to Cloud SQL.
- C.Use gcloud sql import command with a compressed dump file from Cloud Storage.
- ✓ D.Use Database Migration Service with continuous CDC and promote when lag is zero.
Why D: DMS with continuous CDC provides near-zero downtime by replicating ongoing changes. After the initial dump, the source continues to replicate changes, allowing a quick cutover with minimal downtime.
Last reviewed: Jul 4, 2026
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