DBS-C01 Deployment and Migration Practice Test 4 — 15 Questions

Question 1

A company is migrating a 4 TB Oracle database to Amazon Aurora PostgreSQL using AWS DMS. The migration completes successfully but the application experiences high latency on the Aurora cluster. The DMS task used LOB mode 'full LOB mode'. What is the most likely cause of the latency?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Full LOB mode caused large LOBs to be stored in the Aurora cluster, leading to increased I/O. Full LOB mode in AWS DMS loads entire LOBs into memory before writing them to the target, which can cause large LOBs to be stored in the Aurora cluster. This increases I/O and storage overhead, leading to high latency on the Aurora cluster, especially if the LOBs are significantly larger than the default chunk size or if the cluster's I/O capacity is exceeded.

Answer

The Aurora cluster was underprovisioned for parallel load

Answer

The DMS task was configured with 'ongoing replication' causing continuous write load

Answer

The DMS task replicated data to a different region, causing network latency

Question 2

A company uses a self-hosted MySQL database on EC2. They want to migrate to Amazon RDS for MySQL with minimal downtime and automated failover. Which migration strategy should be used?

Accepted Answer

Set up MySQL replication from EC2 to RDS, then cut over. Setting up MySQL native replication from the EC2-hosted MySQL database to an Amazon RDS for MySQL instance allows for near-zero downtime migration. Once replication is established and lag is minimal, you can simply stop writes on the source, verify replication has caught up, and redirect traffic to the RDS endpoint. This approach also supports automated failover by enabling Multi-AZ on the RDS instance, which provides a synchronous standby replica in a different Availability Zone.

Answer

Use mysqldump to export the database and import to RDS

Answer

Take a snapshot of the EC2 instance and restore to RDS

Answer

Use AWS DMS with full load and CDC

Question 3

A company needs to migrate a 100 GB on-premises SQL Server database to Amazon RDS for SQL Server. The migration must be completed within a 4-hour maintenance window. The network link has 500 Mbps throughput. Which approach should be used?

Accepted Answer

Use native SQL Server backup to S3, then restore to RDS. Native SQL Server backup to S3 and restore to RDS is the fastest method for a 100 GB database over a 500 Mbps link. At 500 Mbps, the theoretical transfer time for 100 GB is approximately 28 minutes (100 GB * 8 / 500 Mbps), well within the 4-hour window, making Snowball unnecessary. This approach avoids the overhead of change data capture (CDC) and additional compute resources, directly leveraging SQL Server's native backup/restore capabilities.

Answer

Use AWS DMS with full load and CDC

Answer

Use AWS Snowball Edge to transfer the backup

Answer

Launch an EC2 instance with SQL Server, copy the database, and then migrate to RDS

Question 4

A company has a 200 GB PostgreSQL database on-premises and wants to migrate to Amazon RDS for PostgreSQL. The company requires encrypted data transfer and wants to minimize downtime. Which combination of services should be used?

Accepted Answer

Use AWS DMS with SSL and ongoing replication. AWS DMS with SSL provides encrypted data transfer and supports ongoing replication (change data capture) to minimize downtime. This allows the on-premises PostgreSQL database to remain operational during the initial full load and then continuously replicate changes until cutover, meeting both security and minimal-downtime requirements.

Answer

Use native pg_dump to S3, then import to RDS

Answer

Use AWS VPN to connect on-premises to RDS and perform a database dump

Answer

Use an EC2 instance with PostgreSQL replication to RDS

Question 5

A company is migrating a 5 TB Oracle database to Amazon Aurora MySQL using AWS DMS. The full load completes successfully, but the CDC phase is slow and the target Aurora cluster is consuming high CPU. The DMS instance type is dms.c4.2xlarge. Which change will most likely improve CDC performance?

Accepted Answer

Increase the number of parallel apply threads in the DMS task. Increasing the number of parallel apply threads in the DMS task allows the CDC phase to apply multiple transactions concurrently to the target Aurora cluster, reducing the backlog of changes. The high CPU on the target suggests the apply process is the bottleneck, not the source or network, and DMS's parallel apply threads directly address this by enabling multi-threaded writes, which improves throughput without requiring larger instances.

Answer

Increase the Aurora cluster's max_connections parameter

Answer

Increase the DMS task's target storage allocation

Answer

Change the Aurora cluster to a larger instance class

Question 6

Which THREE actions should be taken to prepare for a migration of an on-premises MySQL database to Amazon RDS for MySQL with minimal downtime using AWS DMS?

Accepted Answer

Enable binary logging on the source MySQL database. Option A is correct because AWS DMS requires binary logging (log_bin enabled, with binlog_format set to ROW and a suitable binlog retention period) on the source MySQL instance to perform ongoing change data capture (CDC) for near-zero-downtime replication. Option B is correct because the DMS replication instance must reach the on-premises MySQL source over the network, so a secure path such as an SSH tunnel, VPN, or AWS Direct Connect is needed for connectivity. Option C is correct because the DMS source user needs REPLICATION CLIENT (to read binary log positions) and REPLICATION SLAVE (to read the binary log stream) privileges, plus SELECT on the tables being migrated, to run full load and CDC. Option D is not required because disabling foreign key checks is not a DMS prerequisite and would risk referential integrity; DMS handles constraints during load. Option E is not required as a DMS preparation step because DMS reads directly from the live source via full load plus CDC, and a separate full backup is not needed for the migration itself.

Answer

Disable foreign key checks on the source database

Answer

Take a full backup of the source database

Question 7

Refer to the exhibit. An IAM policy is attached to a user who will manage AWS DMS tasks. When the user tries to start a replication task, they receive an access denied error. What is the most likely cause?

Accepted Answer

The policy is missing permissions to describe endpoints and connections. The DMS API requires that a user have permissions to describe endpoints and connections before starting a replication task. Even if the policy grants dms:StartReplicationTask, the service internally calls dms:DescribeEndpoints and dms:DescribeConnections to validate the source and target endpoints. Without those describe permissions, the API call fails with an access denied error, even though the start action itself is allowed.

Answer

The policy does not allow rds:DescribeDBInstances

Answer

The policy does not allow the dms:StartReplicationTask action

Answer

The policy does not allow dms:CreateReplicationTask

Question 8

Refer to the exhibit. A DBA is monitoring a DMS migration task from on-premises Oracle to Amazon RDS for Oracle. The full load completed successfully with 50 tables. However, the DBA notices that the CDC phase has not started. What is the most likely reason?

Accepted Answer

The replication task was stopped after the full load completed. The most likely reason the CDC phase has not started is that the replication task was stopped after the full load completed. In AWS DMS, after the full load finishes, the task must remain in a running state to transition to the CDC phase. If the task is stopped, CDC cannot begin, and the DBA would need to resume or restart the task to capture ongoing changes.

Answer

The task was not configured with CDC enabled

Answer

The full load encountered errors on some tables

Answer

The source Oracle database is not generating redo logs

Question 9

A company wants to migrate a 2 TB Amazon RDS for MySQL DB instance to Amazon Aurora MySQL. The migration must have zero downtime and must be reversible for 48 hours. Which strategy meets these requirements?

Accepted Answer

Create an Aurora MySQL Read Replica from the RDS MySQL instance, then promote the replica to a standalone Aurora cluster.. Creating an Aurora MySQL Read Replica from an RDS MySQL instance uses MySQL's native asynchronous replication to keep the Aurora cluster in sync with the source, allowing a near-zero-downtime cutover by promoting the replica. The migration is fully reversible within 48 hours because the original RDS instance remains unchanged and can continue serving traffic if the promotion is rolled back.

Answer

Take a snapshot of the RDS MySQL instance, restore it to Aurora MySQL, and update the DNS.

Answer

Export the database using mysqldump, import into Aurora, and switch DNS.

Answer

Use AWS DMS with ongoing change data capture (CDC) to migrate to Aurora.

Question 10

A company is migrating a 1 TB Amazon RDS for Oracle database to Amazon RDS for PostgreSQL. The migration must be completed within a 4-hour maintenance window. The database has a high volume of transactions. Which migration method minimizes risk of data loss?

Accepted Answer

Use AWS DMS with a full load and change data capture (CDC) enabled, with task restart and validation.. AWS DMS with full load and CDC enables continuous replication of ongoing transactions after the initial load, minimizing data loss risk during the migration window. The task restart and validation features ensure resilience against transient failures and data integrity checks, critical for a high-volume transactional database. This approach meets the 4-hour window by allowing the full load to complete within the window while CDC captures any changes that occur during and after the load.

Answer

Use AWS SCT to convert the schema, then use AWS DMS for full load and ongoing replication.

Answer

Set up Oracle log shipping to an EC2 instance, then restore to RDS PostgreSQL.

Answer

Export the Oracle database using Data Pump, import to PostgreSQL using pgloader.

Question 11

A company is migrating a 10 TB Amazon RDS for MySQL database to Amazon Aurora MySQL. The migration must have minimal downtime and must support point-in-time recovery for the source during migration. Which approach meets these requirements?

Accepted Answer

Create a read replica of the source RDS instance, use AWS DMS with CDC from the read replica to Aurora, then promote Aurora.. Creating a read replica of the source RDS for MySQL instance and using AWS DMS with Change Data Capture (CDC) from that replica allows the migration to proceed with minimal downtime. The read replica offloads the CDC overhead from the source, and CDC captures ongoing changes after the full load, enabling a near-zero-downtime cutover. Additionally, the source RDS instance remains fully available for point-in-time recovery (PITR) throughout the migration, as the read replica does not interfere with the source's backup or transaction log retention.

Answer

Use mysqldump to export the database, import into Aurora, and point DNS to Aurora.

Answer

Use AWS DMS with CDC directly from the source RDS instance to Aurora.

Answer

Take a snapshot of the source RDS instance, restore to Aurora, and point DNS to Aurora.

Question 12

A company is migrating an on-premises PostgreSQL database to Amazon RDS for PostgreSQL. Which TWO AWS services can be used to assess the source database for compatibility and migration readiness?

Accepted Answer

AWS Schema Conversion Tool (SCT). AWS Schema Conversion Tool (SCT) is designed to assess source databases for compatibility by analyzing the schema, code objects, and dependencies, then generating a detailed assessment report that identifies conversion complexity and migration readiness. For PostgreSQL to Amazon RDS for PostgreSQL migrations, SCT validates that the source schema is compatible with the target RDS engine version and highlights any deprecated features or required modifications.

Answer

Amazon Kinesis

Answer

AWS Glue

Answer

Amazon CloudWatch

Question 13

A company is deploying a new Amazon RDS for Oracle database in a VPC. The database must be accessed by an application running on an EC2 instance in a different subnet. Which THREE steps are required to allow this access?

Accepted Answer

Configure the network ACL for the RDS subnet to allow inbound traffic from the EC2 subnet.. Option C is correct because network ACLs are stateless subnet-level firewalls, so the RDS subnet's NACL must explicitly allow inbound traffic from the EC2 instance's subnet CIDR on the Oracle listener port (1521) for the connection to reach the DB instance. Option D is correct because RDS provisions the instance with a DNS endpoint, and the 'Enable DNS hostnames' attribute must be true in the VPC for that endpoint to resolve to an IP address the application can connect to. Option E is correct because security groups are stateful instance-level firewalls, and adding an inbound rule to the RDS security group that references the EC2 instance's security group as the source permits the application's traffic on the database port. Option A is not required because both instances are already in the same VPC, so no VPC peering connection is needed. Option B is not required because the traffic stays within the VPC and does not traverse the internet, so an Internet Gateway is unnecessary.

Answer

Create a VPC peering connection between the subnets.

Answer

Attach an Internet Gateway to the VPC.

Question 14

Refer to the exhibit. An IAM policy is attached to an IAM user that performs database migrations. When the user tries to start an AWS DMS replication task that writes to the RDS instance 'targetdb', the task fails with an access denied error. Which additional permission is required?

Accepted Answer

dms:DescribeReplicationInstances. The DMS replication task requires permission to describe the replication instance that is being used to run the task. The `dms:DescribeReplicationInstances` action allows the IAM user to retrieve metadata about the replication instance, which DMS needs to validate the instance state and configuration before starting the task. Without this permission, the start task operation fails with an access denied error even if the user has permissions to start the task itself.

Answer

dms:CreateEndpoint

Answer

dms:CreateReplicationInstance

Answer

rds:ModifyDBInstance on the source database

Question 15

Refer to the exhibit. A database specialist is taking a final snapshot of an RDS DB instance before deletion. The command returns the output shown. The snapshot is at 75% progress. What should the specialist do next?

Accepted Answer

Wait for the snapshot status to become 'available' before deleting the instance.. An RDS DB instance cannot be deleted while a final snapshot is in progress; the snapshot must reach the 'available' status first. The AWS CLI output shows the snapshot at 75% progress, meaning the snapshot is still being created. Attempting to delete the instance before the snapshot completes will result in an error, as the deletion operation requires the snapshot to be fully available.

Answer

Use the describe-db-snapshots command with --db-snapshot-identifier to get more details.

Answer

Use the stop-db-instance command to pause the snapshot.

Answer

Delete the DB instance immediately; the snapshot will continue in the background.