DBS-C01 Practice Test 38 — 15 Questions

Question 1

A company is migrating a PostgreSQL database to Amazon Aurora PostgreSQL. To minimize downtime, they plan to use the AWS DMS with change data capture (CDC). During the full load phase, DMS reports an error: 'Failed to add foreign key constraint'. What is the most likely cause?

Accepted Answer

Referential integrity violations in the source data. Option B is correct because DMS disables foreign key constraints during full load to speed up data transfer, then re-enables them. If the data violates constraints, it fails. Option A is wrong because DMS handles data type conversions automatically. Option C is wrong because CDC is not the issue. Option D is wrong because DMS doesn't require a primary key in the target during full load.

Answer

CDC is incompatible with foreign key constraints

Answer

The target table lacks a primary key

Answer

Data type mismatch between source and target

Question 2

A company is deploying a new multi-AZ application that requires a relational database. The database must be highly available and must automatically failover to a standby in another Availability Zone within minutes. The database size is 500 GB and the workload is read-heavy. Which AWS RDS configuration meets these requirements?

Accepted Answer

Deploy Amazon RDS for MySQL with Multi-AZ and a read replica in a different AZ. Amazon RDS Multi-AZ deployment provides automatic failover to a standby in another AZ. Option B is incorrect because Multi-AZ is not available for Aurora; Aurora uses a cluster with a primary and readers. Option C is incorrect because cross-Region replicas are for disaster recovery, not automatic failover in the same Region. Option D is incorrect because RDS Proxy is for connection pooling, not high availability.

Answer

Deploy Amazon Aurora with Multi-AZ

Answer

Deploy Amazon RDS for PostgreSQL with a cross-Region read replica

Answer

Deploy Amazon RDS for Oracle with RDS Proxy

Question 3

After migrating a database to Amazon RDS, an application on an EC2 instance in the same VPC cannot connect. The command in the exhibit shows the endpoint. What is the most likely cause?

Accepted Answer

The security group for the DB instance does not allow inbound traffic from the EC2 instance's security group.. Option B is correct because the most common issue is security group rules not allowing inbound traffic on the database port from the EC2 instance. Option A is wrong because the endpoint is correct. Option C is wrong because the RDS instance is in the same VPC, so no VPN is needed. Option D is wrong because public accessibility is not required for same VPC connectivity.

Answer

The EC2 instance is in a different VPC and needs a VPN connection.

Answer

The DB instance endpoint is incorrect.

Answer

The DB instance is not publicly accessible.

Question 4

A company is migrating a 500 GB SQL Server database to Amazon RDS for SQL Server. They need to minimize downtime. Which TWO actions should they take? (Choose two.)

Accepted Answer

Use AWS DMS with ongoing change data capture (CDC). Option A (DMS with CDC) and Option B (Migrate to Multi-AZ after migration) are correct. Option C (S3) is not needed. Option D (Direct Connect) improves bandwidth but not necessary for minimal downtime. Option E (SCT) is for schema conversion, not needed if schema is compatible.

Answer

Store database backup files in Amazon S3

Answer

Use AWS Schema Conversion Tool to convert the schema

Answer

Set up AWS Direct Connect for the migration

Question 5

A company is deploying a new web application that uses Amazon RDS for MySQL. To meet high availability requirements, the database must automatically failover to a standby in a different Availability Zone with minimal downtime. Which deployment configuration should be used?

Accepted Answer

Multi-AZ deployment with automatic failover. Option A is correct because a Multi-AZ deployment automatically creates a standby in a different AZ and handles failover. Option B is wrong because read replicas are for read scaling, not automatic failover. Option C is wrong because a single-AZ deployment does not provide automatic failover. Option D is wrong because a cluster configuration exists for Aurora, not standard RDS for MySQL.

Answer

Single-AZ deployment with enhanced monitoring

Answer

Multi-AZ cluster deployment

Answer

Single-AZ deployment with a read replica

Question 6

A company is deploying a MySQL RDS instance using this CloudFormation template. After deployment, they notice that the database is not automatically backed up at the scheduled time. What is the most likely cause?

Accepted Answer

The BackupRetentionPeriod must be greater than 0 to enable automated backups; however, it is set to 7, so this is not the issue. The actual cause might be that the DB instance is using a storage engine not supported for backups (e.g., MyISAM).. Option C is correct because to enable automated backups, the BackupRetentionPeriod must be greater than 0. In the snippet, it is set to 7, so backups should be enabled. However, automated backups are only supported for InnoDB storage engine; if the instance uses MyISAM, backups may fail. But the question asks for most likely cause; another common issue is that the backup window is too short or conflicts with maintenance, but the snippet shows valid windows. Option A is wrong because MultiAZ does not affect backups. Option B is wrong because storage type gp2 supports backups. Option D is wrong because the backup window is defined.

Answer

The storage type gp2 does not support automated backups.

Answer

The PreferredBackupWindow is not defined, so backups are disabled.

Answer

MultiAZ is enabled, which disables automated backups.

Question 7

A company needs to migrate a 1 TB Oracle database to Amazon RDS for Oracle. The migration must have minimal downtime and the source database is running on-premises. Which TWO AWS services should be used together to achieve this?

Accepted Answer

AWS Database Migration Service (DMS). Options B and D are correct. AWS DMS (B) can perform the initial full load and ongoing replication, while AWS SCT (D) can help convert the Oracle schema to be compatible with RDS. Option A is wrong because Snowball is for large offline data transfer, not for minimal downtime migration with ongoing replication. Option C is wrong because Direct Connect is a network service, not a migration service. Option E is wrong because CloudEndure is for server migration, not database migration.

Answer

AWS CloudEndure Migration

Answer

AWS Snowball

Answer

AWS Direct Connect

Question 8

A company is migrating a 1 TB SQL Server database to Amazon RDS for SQL Server. They need to minimize downtime and support ongoing replication. Which combination of AWS services should they use?

Accepted Answer

AWS SCT and AWS DMS. Option C is correct because AWS DMS supports ongoing replication and SCT helps convert the schema. Option A is wrong because native backup/restore does not support ongoing replication. Option B is wrong because S3 is not directly involved in database replication. Option D is wrong because DMS alone does not handle schema conversion.

Answer

AWS S3 and AWS Glue

Answer

AWS DMS alone

Answer

Native SQL Server backup and restore to RDS

Question 9

A developer is deploying an application that uses Amazon DynamoDB as its database. The application experiences sudden spikes in traffic. Which DynamoDB feature should the developer use to handle the spikes without manual intervention?

Accepted Answer

DynamoDB auto scaling. DynamoDB auto scaling adjusts capacity based on traffic patterns. Option A is incorrect because on-demand capacity is suitable for unpredictable workloads but may be more expensive. Option C is incorrect because DAX is a caching layer, not a scaling feature. Option D is incorrect because global tables are for multi-Region replication.

Answer

DynamoDB Accelerator (DAX)

Answer

DynamoDB on-demand capacity mode

Answer

DynamoDB global tables

Question 10

A company wants to migrate an on-premises MySQL database to Amazon RDS for MySQL with minimal downtime. The database is 500 GB and has moderate write activity. Which approach is MOST suitable?

Accepted Answer

Use AWS Database Migration Service (DMS) with a full load and ongoing replication.. Option C is correct because AWS DMS with ongoing replication allows continuous data synchronization from on-premises to RDS, enabling a cutover with minimal downtime. Option A is wrong because taking a snapshot of the on-premises database and restoring to RDS would require downtime during backup and restore, and does not capture ongoing changes. Option B is wrong because AWS Database Migration Service (DMS) supports homogeneous migrations like MySQL to MySQL, not just heterogeneous. Option D is wrong because exporting to a dump file and importing requires downtime and does not handle ongoing writes.

Answer

Use mysqldump to export the database, then import into RDS.

Answer

Use AWS Server Migration Service (SMS) to migrate the database server.

Answer

Create a read replica of the on-premises database and promote it to RDS.

Question 11

A company is migrating a 2 TB Oracle database to Amazon Aurora PostgreSQL. They need to minimize downtime. Which AWS service should they use?

Accepted Answer

AWS Database Migration Service (DMS). AWS Database Migration Service (DMS) supports heterogeneous migrations from Oracle to Aurora PostgreSQL and can perform ongoing replication to minimize downtime. Option A is correct. Option B (AWS Snowball) is for large data transfer but not for ongoing replication. Option C (SCT) helps with schema conversion but not data migration. Option D (Data Pipeline) is not designed for database migrations.

Answer

AWS Schema Conversion Tool (SCT)

Answer

AWS Data Pipeline

Answer

AWS Snowball

Question 12

A company is deploying a new application using Amazon DynamoDB. They need to ensure data durability and availability. Which THREE steps should they take? (Choose three.)

Accepted Answer

Configure Auto Scaling for read and write capacity. Option A (DAX) improves performance, not durability. Option B (Point-in-time recovery) provides durability. Option C (Auto Scaling) ensures availability. Option D (Global Tables) provides multi-region durability and availability. Option E (Encryption) is for security.

Answer

Enable DynamoDB Accelerator (DAX)

Answer

Encrypt data at rest using AWS KMS

Question 13

A company is migrating a 1 TB SQL Server database to Amazon RDS for SQL Server. They use AWS DMS with full load and ongoing replication. After the full load completes, they observe that the ongoing replication is falling behind and the target database is not consistent. The source database has high transaction volume. What is the most effective way to improve replication performance?

Accepted Answer

Increase the size of the DMS replication instance (e.g., from dms.c5.xlarge to dms.c5.2xlarge).. Option D is correct because increasing the replication instance size provides more CPU and memory, which can handle higher volumes of changes. Option A is wrong because parallel load tasks apply to full load, not ongoing replication. Option B is wrong because batch apply can help but may not be sufficient if the instance is underpowered. Option C is wrong because disabling logging reduces fault tolerance but does not improve replication speed.

Answer

Disable CloudWatch logging for the DMS replication instance.

Answer

Configure multiple parallel load tasks for ongoing replication.

Answer

Enable batch apply mode in the DMS task.

Question 14

A company is migrating an on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The database is 2 TB in size and has a sustained write rate of 50 MB/s. The migration must have minimal downtime. Which migration approach should be used?

Accepted Answer

Use AWS DMS with ongoing replication (change data capture). Option D is correct because AWS Database Migration Service (DMS) with ongoing replication allows minimal downtime by continuously replicating changes from the source to the target. Option A is wrong because AWS DMS with full load only does not support ongoing replication, leading to downtime. Option B is wrong because pg_dump/pg_restore is a logical backup tool that requires downtime during the dump and restore process. Option C is wrong because an RDS read replica can only be created from an existing RDS instance, not from on-premises.

Answer

Create an RDS read replica from the on-premises database

Answer

Use pg_dump and pg_restore

Answer

Use AWS DMS with a full-load task only

Question 15

A company is deploying an Amazon DynamoDB table with on-demand capacity mode. The table will be accessed from multiple AWS Regions and requires strong consistency. Which THREE steps should be taken to meet these requirements?

Accepted Answer

Create a global secondary index. Options A, B, and D are correct. DynamoDB global tables (A) provide multi-region deployment, but they only support eventual consistency; however, for strong consistency, you need to use DynamoDB global tables with strong consistency (B) which is available in some regions, and you must have a global secondary index (D) to support strong consistent reads. Option C is wrong because DynamoDB Accelerator (DAX) is a caching layer that does not provide strong consistency across regions. Option E is wrong because auto scaling is not needed when using on-demand capacity mode.

Answer

Use DynamoDB Accelerator (DAX)

Answer

Configure auto scaling