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Zorluk: OrtaDatabase Migration and Schema Conversion using DMS and SCT

A solutions architect is migrating an on-premises Microsoft SQL Server database to Amazon RDS for PostgreSQL using the AWS Schema Conversion Tool (SCT) and the AWS Database Migration Service (DMS). The migration strategy requires minimal downtime, so the architect configures a DMS replication task with full load and ongoing replication (Change Data Capture). The full load phase completes successfully, and all initial data is copied to the target database. However, the task immediately fails and halts when attempting to replicate subsequent transactional updates. What is the most likely cause of this replication failure?

  1. A
    The target Amazon RDS for PostgreSQL database parameter group does not have the rds.logical_replication parameter set to 1.
  2. B
    The AWS Schema Conversion Tool (SCT) agent has not been deployed on the target database instance to dynamically convert the incoming T-SQL transaction logs into PL/pgSQL during the replication phase.
  3. The source Microsoft SQL Server database does not have MS-CDC or MS-Replication enabled, and the SQL Server Agent is not running on the source host.Cevap
  4. D
    The DMS replication task target endpoint has supplemental logging enabled, preventing PostgreSQL from writing incoming changes to its Write-Ahead Log (WAL).

Cevap

The source Microsoft SQL Server database does not have MS-CDC or MS-Replication enabled, and the SQL Server Agent is not running on the source host.
The correct answer is that the source Microsoft SQL Server database does not have MS-CDC or MS-Replication enabled, or the SQL Server Agent service is not running. AWS DMS requires these source-side database configurations to parse transaction logs and capture ongoing changes. Because the full load phase completed successfully, basic network connectivity and table structures are verified, leaving the lack of CDC setup on the source as the primary cause of the replication failure.

Adım Adım Çözüm

1
Analyze the migration failure phase.
The full load phase completed successfully, meaning network connectivity, credentials, and initial schema application are correct, but the ongoing replication (CDC) phase failed immediately.
This isolates the issue specifically to AWS DMS's ability to read changes from the source database transaction logs.
2
Identify the source database requirements for AWS DMS Change Data Capture (CDC).
For Microsoft SQL Server sources, AWS DMS requires either MS-CDC (Change Data Capture) or MS-Replication to be enabled, and the SQL Server Agent service must be active to track and log transactional changes.
Without these configurations, SQL Server does not log the transaction changes in a format that AWS DMS can consume, causing the CDC phase to fail.

Anahtar Kavram

AWS DMS requires source-specific logging configurations (such as MS-CDC for SQL Server, binlogs for MySQL, or supplemental logging for Oracle) to support ongoing replication (Change Data Capture).
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Database Migration and Schema Conversion using DMS and SCT

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