DBS-C01 Deployment and Migration Practice Test 12 — 15 Questions

Question 1

A company is migrating an on-premises DynamoDB table to Amazon DynamoDB in another AWS region. What is the most efficient method to migrate the data?

Accepted Answer

Use DynamoDB global tables to replicate data across regions.. DynamoDB global tables provide a fully managed, multi-region, multi-master replication solution that automatically replicates data across AWS regions with low latency. This eliminates the need for custom code or external tools, making it the most efficient method for migrating an on-premises DynamoDB table to another region, as it handles ongoing replication and conflict resolution natively.

Answer

Export the table to S3 using AWS Data Pipeline, then import into DynamoDB in the target region.

Answer

Set up DynamoDB Streams and write a custom consumer to replicate data to the target region.

Answer

Use AWS DMS to replicate data from on-premises to DynamoDB.

Question 2

A company is migrating a 2 TB Oracle database running on an on-premises Linux server to Amazon RDS for Oracle. The migration must have minimal downtime and must be fully reversible if any issues arise. The DBA has configured AWS DMS with a full load and ongoing replication task. The full load completes successfully, and CDC is replicating changes. During the cutover window, the DBA stops the source database and promotes the target RDS instance. However, after cutover, the application team reports that some recent transactions are missing from the target database. The DBA confirms that the DMS task showed a 'healthy' status before stopping. Which action should the DBA take to resolve the issue and prevent recurrence?

Accepted Answer

Before stopping the source database, run the 'Stop task' command with the '--apply-immediately' option to ensure all cached changes are written to the target.. In AWS DMS, after full load completes, ongoing replication (CDC) accumulates changes in a cache. To ensure no data loss during cutover, the DBA should stop the source database and then issue a 'Stop task' command with the '--apply-immediately' option (or use the 'Last Stop' job in the console) to flush all cached changes to the target before stopping the task. Option A (native export/import) would cause significant downtime and is unnecessary. Option B (increasing instance size) improves throughput but does not capture remaining cached changes. Option C (restarting from the beginning) would lose already migrated data and is not a targeted fix. Only option D directly addresses the issue of missing transactions by ensuring all CDC cached changes are applied before the task is stopped.

Answer

Rebuild the entire migration using a native Oracle export/import tool.

Answer

Increase the replication instance size to improve throughput.

Answer

Restart the DMS task from the beginning to recapture the missing data.

Question 3

A company is migrating a 1 TB Microsoft SQL Server database to Amazon RDS for SQL Server using native backup and restore. The DBA has taken a full backup of the source database and uploaded it to an S3 bucket. The DBA then uses the 'aws rds restore-db-instance-from-db-snapshot' CLI command to restore the backup to an RDS instance. The restore fails with an error: 'Could not find the specified backup file in the S3 bucket.' The DBA verifies that the backup file exists in the correct S3 bucket and that the IAM role used by RDS has permissions to access the bucket. What is the most likely cause of the failure?

Accepted Answer

The backup file is not placed in the correct S3 bucket path that includes the account ID prefix.. When restoring a native backup to Amazon RDS for SQL Server, the backup file must be placed in an S3 bucket with a specific path structure that includes the AWS account ID and optionally a prefix. The correct path is typically: s3://bucket-name/account-id/optional-prefix/backup-file.bak. If the file is not in the correct path, RDS cannot locate it, resulting in the error 'Could not find the specified backup file in the S3 bucket.'

Answer

The backup file has an incorrect file extension, such as .trn instead of .bak.

Answer

The backup file is not encrypted with AWS KMS.

Answer

The RDS instance is not configured to use native restore.

Question 4

A company wants to migrate a 500 GB MySQL database from an on-premises server to Amazon RDS for MySQL. The migration must be completed within a 2-hour downtime window. Which migration approach is MOST suitable?

Accepted Answer

Create a compressed backup using Percona XtraBackup, upload it to S3, and restore it to RDS.. Percona XtraBackup allows you to create a physical backup of the MySQL database that can be compressed and uploaded to Amazon S3, then restored directly to an Amazon RDS for MySQL instance. This approach is significantly faster than logical backups (like mysqldump) for a 500 GB database, as it bypasses SQL parsing and rebuilds the data files directly, enabling completion within a 2-hour downtime window.

Answer

Use AWS Database Migration Service (DMS) with a full load.

Answer

Use mysqldump to export the database and then import it into RDS.

Answer

Create an RDS Read Replica of the on-premises database and promote it.

Question 5

A company is migrating a 1 TB Microsoft SQL Server database from on-premises to Amazon RDS for SQL Server. The on-premises database uses TDE for encryption. The company must ensure that the migrated database in RDS also uses TDE. Which solution meets this requirement?

Accepted Answer

Use AWS DMS with ongoing replication to an RDS instance that has TDE enabled.. AWS DMS can migrate data from an on-premises SQL Server database with TDE enabled to an Amazon RDS for SQL Server instance that has TDE enabled. DMS reads the decrypted data from the source (since TDE is transparent to applications) and writes it to the target, which can then encrypt the data at rest using RDS's built-in TDE support. This approach avoids the need to transfer TDE certificates or perform a native backup/restore, which are not supported for TDE-enabled databases in RDS.

Answer

Export the on-premises database with TDE certificates and import them into RDS.

Answer

Take a native backup of the on-premises database with TDE, upload to S3, and restore to RDS.

Answer

Use AWS SCT to convert the database to Amazon Aurora and enable encryption.

Question 6

A company is migrating a 2 TB Oracle database to Amazon RDS for Oracle. The database has a large number of stored procedures, triggers, and functions. The company wants to minimize changes to the application code. Which AWS service should be used to assess and convert the database schema?

Accepted Answer

AWS Schema Conversion Tool (SCT). AWS Schema Conversion Tool (SCT) is designed specifically to convert database schemas from one engine to another, including Oracle to Amazon RDS for Oracle. It assesses the source schema, identifies incompatibilities, and automatically converts stored procedures, triggers, and functions to minimize application code changes. SCT also provides action items for any manual remediation needed, ensuring a smooth migration with minimal code rewrites.

Answer

AWS Database Migration Service (DMS)

Answer

AWS CloudEndure Migration

Answer

AWS CodeCommit

Question 7

A company is migrating a 5 TB Oracle database to Amazon RDS for Oracle. The database contains large BFILEs stored in a file system. The company needs to migrate the data with minimal downtime and ensure the BFILEs are migrated. Which THREE steps should the company take?

Accepted Answer

Use AWS SCT to convert any incompatible schema objects.. Option B is correct because AWS Schema Conversion Tool (AWS SCT) is the recommended tool to assess and convert Oracle schema objects that are incompatible with Amazon RDS for Oracle, which is essential for a smooth migration. Option C is correct because RDS for Oracle does not support BFILEs stored on the database server's file system; instead, BFILEs must be moved to Amazon S3 and referenced via Oracle DIRECTORY objects that point to the S3 bucket (using the RDS for Oracle S3 integration), ensuring the BFILE data is migrated and accessible. Option E is correct because AWS DMS can migrate the Oracle database with minimal downtime, and configuring the Oracle source endpoint with the BFILE directory path allows DMS to read and transfer the BFILE data as part of the migration. Option A is not correct because converting BFILEs to BLOBs is not a required or recommended step for RDS for Oracle migration and would alter the data model unnecessarily. Option D is not correct because AWS CloudEndure Migration replicates entire servers (lift-and-shift), which does not target RDS for Oracle and does not address the BFILE migration requirement.

Answer

Replace BFILEs with BLOBs in the source database before migration.

Answer

Use AWS CloudEndure Migration to replicate the entire server.

Question 8

A company is migrating a 200 GB MySQL database to Amazon Aurora MySQL. The migration must be completed within a 1-hour downtime window. Which TWO methods can achieve this?

Accepted Answer

Use Percona XtraBackup to create a physical backup, upload to S3, and restore to Aurora.. Options C and D are correct because both can move a 200 GB MySQL database into Aurora MySQL within a 1-hour downtime window. C: Percona XtraBackup creates a physical backup that can be uploaded to Amazon S3 and restored directly into Aurora MySQL, which is much faster than logical dumps for large datasets and is the standard fast migration path for large MySQL databases. D: mysqldump with parallel threads (e.g., using --parallel or mydumper-style parallel export) plus import via the mysql command can also complete within the window if parallelism is used, since it avoids the overhead of a full logical single-threaded dump. A is not correct because AWS SCT converts schema for heterogeneous migrations and does not by itself provide a fast 200 GB data load within 1 hour. B is not correct because AWS DMS full load only would not meet the 1-hour downtime requirement for 200 GB and lacks ongoing replication to minimize cutover time. E is not correct because an RDS Read Replica cannot be created from an on-premises MySQL database; that feature applies to RDS/Aurora sources, not external on-premises instances.

Answer

Use AWS SCT to convert the schema and then perform a data load.

Answer

Use AWS DMS with full load only.

Answer

Create an RDS Read Replica of the on-premises database and promote it.

Question 9

A company is migrating a 500 GB MySQL database from an on-premises server to Amazon RDS for MySQL. The company uses AWS DMS with ongoing replication. The initial full load completes successfully, and the target RDS instance is in sync. However, after a few hours, the replication task fails with an error: 'Last Error: Error executing source loop; The table 'orders' has a row size larger than the maximum payload size of the target endpoint.' The target RDS instance is configured with db.r5.large and the default parameter group. The company has already verified that the table does not have any BLOB or TEXT columns. What is the MOST likely cause of this error?

Accepted Answer

The source table has a row that exceeds the MySQL row size limit.. The error 'row size larger than the maximum payload size of the target endpoint' from AWS DMS indicates that a single row in the source table exceeds the maximum row size the target MySQL endpoint can accept. Even without BLOB or TEXT columns, a table with many VARCHAR/CHAR columns (especially with utf8mb4 encoding, where each character can take up to 4 bytes) can exceed MySQL's row size limit. The default InnoDB row size limit is approximately 8,000 bytes (half a page), and DMS enforces this when writing to the target.

Answer

The DMS task is using a low-memory instance.

Answer

The target RDS instance's max_allowed_packet parameter is set too low.

Answer

The target RDS instance does not have enough storage allocated.

Question 10

A company is migrating a 100 GB Microsoft SQL Server database from an on-premises data center to Amazon RDS for SQL Server. The migration uses AWS DMS with full load only (no ongoing replication). The full load completes successfully, but the company's application team reports that some data in the target database is missing. The source database was not modified during the migration. The DMS task logs show no errors. What is the MOST likely cause of the missing data?

Accepted Answer

The DMS task did not use transactional consistency.. When AWS DMS performs a full load without transactional consistency, it reads tables in parallel and does not guarantee a consistent snapshot across all tables. If the source database has referential relationships or if data is being written during the load (though the question says it wasn't), inconsistencies can occur. More specifically, without transactional consistency, DMS may read tables at different points in time, leading to missing or orphaned rows in the target. Enabling transactional consistency (or using a consistent snapshot) ensures all tables are read from the same point-in-time.

Answer

The DMS task used the 'Change Data Capture' mode instead of full load.

Answer

The target RDS instance was not large enough to store all data.

Answer

The source database had foreign key constraints that were not migrated.

Question 11

A financial services company is migrating a 500 GB Oracle database to Amazon Aurora MySQL-Compatible Edition. The migration must have minimal downtime and support bidirectional replication for a test-and-cutover approach. The company currently uses Oracle GoldenGate for replication. Which migration strategy should be used?

Accepted Answer

Use AWS DMS with a full load and ongoing replication from Oracle to Aurora MySQL, then cut over.. AWS DMS with full load and ongoing replication is the correct strategy because it supports minimal-downtime migration from Oracle to Aurora MySQL and can handle bidirectional replication for a test-and-cutover approach. DMS uses change data capture (CDC) from Oracle's redo logs to keep the target in sync, allowing you to validate the target before cutting over. This meets the requirement for minimal downtime and a test-and-cutover workflow without relying on Oracle GoldenGate.

Answer

Use AWS Schema Conversion Tool (SCT) to convert the schema and then use AWS DMS for a one-time full load.

Answer

Use AWS DMS with Oracle GoldenGate as a source for continuous replication to Aurora MySQL.

Answer

Use Oracle GoldenGate to replicate directly to Aurora MySQL, then cut over.

Question 12

A company is deploying a new web application that uses Amazon RDS for MySQL. The application must be highly available across three Availability Zones with automatic failover. Which deployment configuration should be used?

Accepted Answer

Deploy Amazon Aurora MySQL with three Aurora Replicas in different Availability Zones.. Amazon Aurora MySQL is the correct choice because it is designed for high availability across three Availability Zones by default, with six copies of data across three AZs and the ability to create up to 15 Aurora Replicas. The requirement for automatic failover across three AZs is met by deploying three Aurora Replicas in different AZs, ensuring continuous availability even if two AZs fail. Standard Amazon RDS for MySQL Multi-AZ only supports a single standby in one other AZ, not three AZs.

Answer

Deploy Amazon RDS for MySQL in a Single-AZ configuration and use an Application Load Balancer.

Answer

Deploy Amazon RDS for MySQL with Multi-AZ and a standby instance in a different Availability Zone.

Answer

Deploy Amazon RDS for MySQL with Read Replicas in two additional Availability Zones.

Question 13

A company is migrating a self-managed MongoDB database to Amazon DocumentDB (with MongoDB compatibility). Which TWO actions should the company take to ensure a successful migration? (Choose two.)

Accepted Answer

Use AWS Schema Conversion Tool (SCT) to convert MongoDB schemas to DocumentDB compatible format.. Option A is correct because AWS Schema Conversion Tool (SCT) can convert MongoDB schemas and indexes into a DocumentDB-compatible format, which is a recommended step when moving from self-managed MongoDB to DocumentDB since the two are not 100% feature-identical. Option C is correct because AWS DMS supports MongoDB as a source and Amazon DocumentDB as a target, and it can perform both a full load and ongoing replication (change data capture) to minimize downtime during the migration. Option B is incorrect because, while DMS can migrate from MongoDB Atlas, the scenario specifies a self-managed MongoDB database, not Atlas, so this does not address the stated source. Option D is incorrect because DMS does not use an Amazon EBS snapshot as a source endpoint for a MongoDB-to-DocumentDB migration. Option E is incorrect because routing data through Amazon DynamoDB adds an unnecessary and unsupported intermediate step; DMS migrates directly from MongoDB to DocumentDB.

Answer

Use AWS Database Migration Service (DMS) to migrate data from MongoDB Atlas to DocumentDB.

Answer

Use AWS DMS with an Amazon EBS snapshot as the source for the migration.

Answer

Use AWS DMS to migrate data from MongoDB to Amazon DynamoDB, then import into DocumentDB.

Question 14

A company is migrating a database using AWS DMS. The IAM policy shown is attached to the DMS replication instance role. When the DMS replication task is created in the us-west-2 region, it fails. What is the most likely cause?

Accepted Answer

The IAM policy restricts the region to us-east-1, but the task is created in us-west-2.. The IAM policy explicitly restricts the region to us-east-1 using the `aws:RequestedRegion` condition key. When the DMS replication task is created in us-west-2, the policy denies the `dms:CreateReplicationTask` action because the region condition fails, causing the task creation to fail. DMS replication tasks require the IAM role to have permissions in the same region where the task is being created.

Answer

The IAM policy does not allow the 'dms:CreateReplicationTask' action.

Answer

The IAM policy does not specify the VPC where the replication instance is deployed.

Answer

The IAM policy does not specify the resource ARN for the replication instance.

Question 15

A database administrator runs the above CLI command. The output shows that 'mydb' is a read replica of 'mydb-source'. The administrator wants to promote 'mydb' to a standalone instance with no downtime. Which action should be taken?

Accepted Answer

Use the promote-read-replica CLI command.. The `promote-read-replica` CLI command is the correct action because it transitions the read replica from a replication slave to a standalone primary DB instance without requiring any downtime. During promotion, RDS stops replication and makes the replica writable, but the instance remains available throughout the process. This is the only method that achieves zero downtime promotion directly.

Answer

Modify the DB instance to enable Multi-AZ, which automatically promotes it.

Answer

Create a snapshot of the read replica and restore it as a new DB instance.

Answer

Modify the DB instance class to a larger size to force promotion.