DBS-C01 Deployment and Migration Practice Test 6 — 15 Questions

Question 1

A company is migrating a 3 TB PostgreSQL database from on-premises to Amazon RDS for PostgreSQL. The migration must have minimal downtime. The on-premises network bandwidth to AWS is 1 Gbps. The database supports a critical application that cannot be stopped for more than 30 minutes. The migration team has set up AWS DMS with ongoing replication using CDC. The initial full load is expected to take 8 hours. During the migration, the DMS task fails with an error indicating that the source database's transaction log is being cleaned before DMS can capture changes. The source database has a transaction log retention period of 24 hours. The migration team notices that the CDC phase falls behind during peak hours. What should the team do to complete the migration successfully within the downtime window?

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

Accepted Answer

Increase the transaction log retention period on the source database and use a larger DMS replication instance. Increasing the transaction log retention period on the source database prevents the log from being cleaned before DMS can capture changes, addressing the error. Using a larger DMS replication instance provides more resources to handle the CDC load during peak hours, reducing lag. Together, these actions allow the migration to complete within the 30-minute downtime window.

Answer

Use AWS Snowball to transfer the full database and then use DMS for CDC

Answer

Increase the network bandwidth using AWS Direct Connect

Answer

Decrease the transaction log retention period to free up space

Question 2

A company is deploying a new web application on AWS. The application uses Amazon RDS for MySQL as its database. The database must be highly available and automatically failover in the event of an AZ outage. The company also needs to offload read traffic from the primary database to improve performance. The application read-to-write ratio is 80:20. The database workload is variable, with occasional spikes. The company wants a cost-effective solution that scales read capacity automatically. The operations team has limited experience with AWS. Which solution should the company implement?

Accepted Answer

Deploy an Amazon Aurora MySQL cluster with Multi-AZ and enable Aurora Auto Scaling for read replicas. Amazon Aurora MySQL provides Multi-AZ high availability with automatic failover and supports Aurora Auto Scaling, which adds and removes read replicas based on metrics like CPU utilization or connections. This directly satisfies the 80:20 read-heavy workload, variable spikes, and cost-effective automatic scaling requirements with minimal operational overhead. Aurora's managed nature also suits a team with limited AWS experience.

Answer

Deploy an RDS for MySQL instance with Multi-AZ and one or more read replicas, and use Application Auto Scaling to add replicas based on CPU utilization

Answer

Deploy an RDS for MySQL instance with Multi-AZ and enable automatic scaling of the instance size

Answer

Deploy an RDS for MySQL instance with multiple read replicas and use a custom script to promote a read replica in case of failure

Question 3

A company is migrating a 500 GB Oracle database to Amazon RDS for Oracle. The migration must be completed within 24 hours with minimal downtime. The on-premises network bandwidth is 1 Gbps. The migration team plans to use AWS DMS with ongoing replication. During the initial load, the DMS task fails with an error indicating that the source database is experiencing high CPU utilization. The source database is a production system serving live traffic. The team needs to reduce the impact on the source database while still meeting the migration deadline. Which approach should the team take?

Accepted Answer

Reduce the number of tables loaded in parallel in the DMS task and schedule the migration during off-peak hours. The DMS task failed due to high CPU utilization on the source production database, which is caused by the initial full load reading many tables in parallel. Reducing the number of tables loaded in parallel decreases the concurrency of read operations on the source, thereby lowering CPU load. Scheduling the migration during off-peak hours further reduces contention with live traffic, allowing the migration to complete within the 24-hour window without impacting production. This approach balances the need to meet the deadline with minimizing impact on the source system.

Answer

Change the DMS task to perform only full load and skip ongoing replication

Answer

Increase the size of the DMS replication instance to speed up the migration

Answer

Use AWS Snowball to transfer the data offline and then use DMS for ongoing replication

Question 4

A company is migrating a 5 TB Oracle database to Amazon Aurora PostgreSQL. The migration must be completed within a weekend. The on-premises network has a 1 Gbps connection to AWS. What is the MOST efficient migration strategy?

Accepted Answer

Use AWS DMS with direct connect to export the Oracle database directly to Aurora. With a 1 Gbps connection, the theoretical maximum transfer rate is ~450 GB/hour, so transferring 5 TB would take about 11 hours, well within a weekend. AWS DMS with Direct Connect provides a dedicated, high-bandwidth path for the migration, making it the most efficient strategy. Snowball Edge (Option D) requires ordering, loading, shipping (1-2 days), and importing, which cannot complete within a weekend. Options A and C are less efficient: S3 Transfer Acceleration adds unnecessary steps, and DMS with CDC is designed for ongoing replication, not initial load.

Answer

Use AWS S3 Transfer Acceleration to upload the database dump to S3 and then load into Aurora

Answer

Use AWS DMS with change data capture over the existing network connection

Answer

Use AWS Snowball Edge to transfer the data and then load into Aurora

Question 5

An administrator is setting up an AWS DMS replication instance and attaches the IAM policy shown in the exhibit. The administrator receives an error that the replication instance cannot be created. Which missing permission is the MOST likely cause?

Accepted Answer

ec2:DescribeSecurityGroups. When creating a DMS replication instance, AWS DMS needs to create and manage network interfaces in the customer's VPC. The `ec2:DescribeSecurityGroups` permission is required for DMS to validate and describe the security groups specified during replication instance creation. Without this permission, the service cannot verify the security group IDs, leading to a creation failure.

Answer

ec2:DescribeVpcPeeringConnections

Answer

ec2:CreateNetworkInterfacePermission

Answer

dms:CreateReplicationInstance

Question 6

A company is migrating a 500 GB SQL Server database to Amazon RDS for SQL Server. The migration must minimize downtime and support ongoing replication. Which TWO AWS services should be used together?

Accepted Answer

AWS Database Migration Service (DMS). AWS Database Migration Service (DMS) is the correct choice because it supports ongoing replication (change data capture) from a source SQL Server database to Amazon RDS for SQL Server with minimal downtime. DMS can perform a full load followed by continuous replication of changes, allowing the source to remain operational during migration.

Answer

AWS Lambda

Answer

AWS Snowball Edge

Answer

AWS RDS SQL Server native backup and restore

Question 7

An administrator is deploying an Amazon RDS for MySQL DB instance and needs to ensure that all connections use SSL. Which parameter should be set on the RDS DB instance?

Accepted Answer

Set require_secure_transport=ON in the DB parameter group. Setting `require_secure_transport=ON` in the DB parameter group enforces that all connections to the RDS MySQL DB instance must use SSL/TLS. This parameter, supported by MySQL 5.7 and later, rejects any non-encrypted connection attempt, ensuring transport layer security for all client-server communication.

Answer

Set ssl_cipher in the DB parameter group

Answer

Set tls_version in the DB parameter group

Answer

Set rds.force_ssl=1 in the DB parameter group

Question 8

A company is migrating a 2 TB Oracle database to Amazon Aurora PostgreSQL. The on-premises database is 2 TB and the network link is 1 Gbps. The migration must complete within 48 hours with minimal data loss. The DBA has extracted the schema using AWS SCT and created an Aurora cluster. The DBA now needs to transfer the data. The DBA tried using AWS DMS over the network but estimates it will take 72 hours due to network overhead. The DBA also considered using an AWS Snowball Edge device but is concerned about the time to order and ship the device. Which approach should the DBA take to meet the deadline?

Accepted Answer

Use AWS Snowball Edge to transfer the database dump and then use DMS for change data capture. It combines the speed of Snowball Edge for the initial bulk data transfer (2 TB) with AWS DMS for ongoing change data capture (CDC) to minimize data loss. Although ordering and shipping a Snowball device takes time, once received, the data transfer is much faster than over a 1 Gbps network, which would take over 48 hours. DMS alone (option A) is estimated to take 72 hours, exceeding the deadline. Option B (S3 upload) still relies on network speed and would be too slow. Option D (full load only) abandons CDC and does not meet the minimal data loss requirement.

Answer

Use AWS DMS with change data capture and optimize the network by enabling compression

Answer

Use AWS S3 to upload the database dump and then load into Aurora

Answer

Use AWS DMS to perform a full load and then stop replication, accepting some data loss

Question 9

A company is deploying a new Amazon RDS for SQL Server DB instance with Multi-AZ. The database will be used by a critical application that requires minimal downtime during failover. The application uses a single connection string with the CNAME of the RDS endpoint. During a recent failover test, the application experienced a 3-minute timeout. The DBA wants to reduce the failover time. The current RDS instance is db.r5.large with 100 GB gp2 storage. The application is hosted on EC2 in the same VPC. Which change would MOST effectively reduce the failover time?

Accepted Answer

Configure the application to use a low TTL for DNS lookups and implement connection retries. The most effective because the 3-minute timeout during failover is likely due to DNS caching on the application side. By configuring the application to use a low TTL (e.g., 5 seconds) for DNS lookups and implementing connection retries with exponential backoff, the application can quickly resolve the new RDS endpoint's IP address after failover and re-establish connectivity promptly. Option A is incorrect because changing to Provisioned IOPS (io1) improves storage performance but does not reduce DNS-related failover time. Option B is incorrect because increasing the instance size does not directly impact failover duration. Option D is incorrect because Multi-AZ already provides automatic failover; a read replica with manual promotion would not reduce failover time and would require additional management.

Answer

Change the storage to Provisioned IOPS (io1)

Answer

Change the instance type to db.r5.xlarge

Answer

Use a read replica with automatic failover

Question 10

A startup is deploying a new web application on AWS. The application uses Amazon RDS for PostgreSQL as its database. The developers need to create the initial schema and load test data. They have a SQL script file that creates tables and inserts 10,000 rows. The DB instance is a db.t3.micro with 20 GB gp2 storage. The developers connect to the RDS instance using pgAdmin from their local machine and run the script. The script fails with a 'connection reset' error after inserting 5,000 rows. What is the MOST likely cause?

Accepted Answer

The security group blocked the connection due to a timeout. The most likely cause is that the connection was terminated by an idle timeout on an intermediate network component (such as a NAT Gateway, which has a default idle timeout of 350 seconds, or the client-side firewall/proxy). Security groups are stateful and do not have configurable timeout settings, so they are not directly responsible. The script's duration likely exceeded the idle timeout, causing a 'connection reset' error. Option A is unlikely because a db.t3.micro can handle inserting 10,000 rows without exhausting memory or CPU credits; the error is network-related, not resource-related. Option B is incorrect because max_connections is sufficient for a single connection. Option C is incorrect because 20 GB storage is far more than needed for 10,000 rows.

Answer

The DB instance ran out of memory or CPU credits due to the intensive script

Answer

The max_connections parameter was set too low

Answer

The storage volume reached its maximum capacity

Question 11

A company is migrating a 5 TB PostgreSQL database from on-premises to Amazon RDS for PostgreSQL. The database has a 24/7 uptime requirement and must be migrated with minimal downtime. The on-premises network bandwidth is 100 Mbps. The migration must be completed within 48 hours. The team has chosen to use AWS Database Migration Service (DMS) with ongoing replication from a change data capture (CDC) source. After setting up the source endpoint, target endpoint, and replication instance, the initial full load takes 30 hours. However, during the CDC phase, the target falls behind by over 2 hours and continues to lag. The replication instance is a dms.c5.large (2 vCPUs, 4 GB memory). The source database is heavily utilized with frequent updates. What should the team do to reduce the CDC lag and meet the migration deadline?

Accepted Answer

Increase the replication instance size to dms.c5.2xlarge.. The CDC lag is likely due to insufficient resources on the replication instance. The dms.c5.large has only 2 vCPUs and 4 GB memory, which may not handle the load of processing changes from a heavily utilized source database. Increasing to dms.c5.2xlarge provides more CPU and memory, allowing DMS to process changes faster and reduce lag. Multi-AZ does not improve performance; it provides high availability. Splitting into multiple tasks could help but may not be sufficient if the instance is the bottleneck. Disabling ongoing replication would cause data loss and is not acceptable for minimal downtime.

Answer

Enable Multi-AZ on the replication instance for better performance.

Answer

Split the migration into multiple DMS tasks for parallel processing.

Answer

Disable ongoing replication and use a one-time full load migration.

Question 12

An organization wants to migrate a 200 GB MySQL database from an on-premises server to Amazon Aurora MySQL. They have a 50 Mbps network connection. The database is 8 hours of downtime. The migration must be completed within 24 hours and costs must be minimized. The team decides to use AWS Database Migration Service (DMS). Which approach best meets the requirements?

Accepted Answer

Use AWS DMS with a full load and ongoing replication to minimize downtime.. AWS DMS with a full load plus ongoing replication (CDC) is the correct choice because it performs the initial bulk copy while continuously capturing changes from the source MySQL binary logs, allowing cutover during the 8-hour downtime window. At 50 Mbps, transferring 200 GB takes roughly 9-10 hours, which fits within the 24-hour window, and DMS is a managed service that minimizes cost compared to provisioning EC2 or using Snowball. This approach satisfies both the downtime and cost requirements.

Answer

Create a mysqldump and transfer it over the network to S3, then restore to Aurora.

Answer

Use AWS Snowball Edge to transfer the data physically.

Answer

Provision a large EC2 instance to run a parallel export and import.

Question 13

A company is migrating a 1 TB SQL Server database to Amazon RDS for SQL Server. The migration window is 4 hours. The on-premises network bandwidth is 1 Gbps. The database is not actively used during the migration window. The team wants to minimize migration time and cost. Which migration strategy is most appropriate?

Accepted Answer

Use AWS DMS with full load only.. AWS DMS with full load only (Option D) is the most appropriate strategy for this migration. With a 1 Gbps network, the theoretical transfer time for 1 TB is about 2.2 hours (1 TB = 8000 Gb, 8000 Gb / 1 Gbps = 8000 seconds ≈ 2.22 hours), well within the 4-hour window. AWS DMS performs a direct, efficient full-load migration without requiring intermediate storage or additional tools. Option A (BCP + DTS) is slower and more complex. Option B (Snowball) adds cost and logistics that are unnecessary given the network speed. Option C (native backup to S3 and restore) requires uploading the backup to S3 first, then restoring to RDS, which is typically slower than DMS's direct streaming approach.

Answer

Use SQL Server BCP utility to export data and then import using DTS.

Answer

Use AWS Snowball to transfer the database files.

Answer

Create a native backup, upload to S3, restore to RDS.

Question 14

A company has a 100 GB MySQL database on an EC2 instance. They want to migrate to Amazon RDS for MySQL with minimal downtime. They have set up replication from the source to the target using MySQL native replication. After enabling replication, the 'Seconds_Behind_Master' value is increasing. The source database is write-heavy. What should the team do to reduce replication lag?

Accepted Answer

Increase the RDS instance size to a larger instance class.. Replication lag in MySQL native replication is often caused by the target (replica) being unable to apply writes as fast as the source generates them. Increasing the RDS instance size provides more CPU, memory, and IOPS, allowing the replica to apply transactions faster and reduce 'Seconds_Behind_Master'. This directly addresses the bottleneck of insufficient replica resources under a write-heavy source.

Answer

Tune the source database to reduce write load.

Answer

Enable Multi-AZ on the RDS instance.

Answer

Switch to AWS DMS for migration.

Question 15

A company is migrating a 500 GB PostgreSQL database from on-premises to Amazon Aurora PostgreSQL. The migration must be completed within 6 hours with minimal downtime. The on-premises network bandwidth is 500 Mbps. The team decides to use AWS DMS. During initial full load, DMS reports a 'Target metadata error: cannot write to Aurora' for a specific table. Investigation shows that the table has a trigger that tries to insert into an external web service. What should the team do to resolve this issue?

Accepted Answer

Disable the trigger on the target Aurora database during migration.. Disabling the trigger on the target Aurora PostgreSQL database during migration prevents the trigger from firing, which was causing the 'Target metadata error: cannot write to Aurora' error. The trigger's attempt to insert into an external web service is not compatible with DMS loading data. Option B is incorrect because increasing the DMS replication instance size does not address the trigger issue. Option C is incorrect because upgrading the DMS replication instance engine version does not address the trigger issue. Option D is incorrect because disabling the trigger on the source database does not prevent the trigger on the target from firing when DMS writes data; the error occurs on the target.

Answer

Increase the DMS replication instance size.

Answer

Upgrade the DMS replication instance engine version.

Answer

Disable the trigger on the source database.