DBS-C01 Deployment and Migration Practice Test 23 — 15 Questions

Question 1

A company is migrating a PostgreSQL database to Amazon Aurora PostgreSQL. They want to use the AWS DMS for the migration. Which THREE resources need to be created in the AWS account?

Accepted Answer

DMS target endpoint pointing to Aurora PostgreSQL.. AWS DMS requires a target endpoint that specifies the connection details for the Amazon Aurora PostgreSQL database. This endpoint tells DMS where to load the migrated data, and it must be configured with the correct database name, credentials, and VPC settings to ensure successful connectivity during the migration task.

Answer

Application Load Balancer for the replication instance.

Answer

AWS CloudFormation stack to provision resources.

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 from S3 to RDS, the backup file must be stored in a path that includes the AWS account ID as a prefix (e.g., /123456789012/backup.bak). RDS for SQL Server expects this specific path structure to locate the file. Even if the file exists in the bucket and permissions are correct, a wrong path causes the 'Could not find the specified backup file' error. Option A is wrong because the file extension is not the issue; RDS accepts .bak and .trn files. Option B is wrong because encryption is not required for native restore. Option C is wrong because native restore is a supported feature on RDS for SQL Server; the error is about file location, not configuration.

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 is migrating a 500 GB MongoDB database to Amazon DocumentDB. The migration is done using AWS DMS with full load and ongoing replication. The full load completes successfully, but during CDC, the DMS task logs show 'Memory limit exceeded' errors and the task fails repeatedly. The DMS replication instance is a dms.r5.large. The source MongoDB has a write-heavy workload with many small updates. The DBA needs to fix the migration without restarting from scratch. Which action should the DBA take?

Accepted Answer

Increase the DMS replication instance size to a larger instance class with more memory.. The 'Memory limit exceeded' error during CDC with a write-heavy workload indicates the replication instance lacks sufficient memory to buffer the changes. Increasing the instance size (e.g., to dms.r5.xlarge) provides more memory. Option B is wrong because reducing BatchApplyEnabled may slow down apply but does not increase memory; it could even worsen the backlog. Option C is wrong because restarting just clears cache temporarily; the error will recur. Option D is wrong because Multi-AZ provides high availability, not additional memory.

Answer

Reduce the DMS task's 'BatchApplyEnabled' setting to apply transactions individually.

Answer

Stop and restart the DMS task to clear the cache.

Answer

Enable Multi-AZ on the DMS replication instance to distribute the load.

Question 5

A company is migrating a 2 TB Oracle database from on-premises to Amazon RDS for Oracle. The database has a 4-hour maintenance window and the migration must have minimal downtime. Which AWS service should be used for the migration?

Accepted Answer

Use AWS Database Migration Service (DMS) with ongoing replication from the source database.. AWS DMS with ongoing replication (change data capture) is the correct choice because it allows you to perform a full load of the 2 TB Oracle database and then continuously replicate incremental changes from the source to the target RDS instance. This minimizes downtime by enabling a cutover window of minutes rather than hours, which is critical given the 4-hour maintenance window constraint.

Answer

Use AWS Schema Conversion Tool (SCT) to convert the schema and then perform a full data load.

Answer

Create an RDS Cross-Region Read Replica and promote it to a standalone instance.

Answer

Take a full backup of the on-premises database, upload it to S3, and restore it to RDS.

Question 6

A company is planning to migrate a 3 TB PostgreSQL database from an on-premises data center to Amazon Aurora PostgreSQL. The migration must have near-zero downtime. The on-premises database is using a custom pg_hba.conf that restricts access to specific IP ranges. Which combination of steps will meet the requirements?

Accepted Answer

Use AWS DMS with ongoing replication to an Aurora DB cluster. Configure the source endpoint with the appropriate connection settings.. AWS DMS with ongoing replication (CDC) enables near-zero downtime migration by continuously synchronizing changes from the source PostgreSQL database to the target Aurora PostgreSQL cluster after an initial full load. Configuring the source endpoint with the correct connection settings, including the custom pg_hba.conf IP ranges, allows DMS to connect securely. This approach meets the requirement for minimal downtime, unlike batch export/import methods.

Answer

Create an Aurora Replica of the on-premises database using cross-Region replication.

Answer

Use pg_dump and pg_restore to export and import the database during a maintenance window.

Answer

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

Question 7

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 8

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 9

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 10

A company is migrating a 100 GB MySQL database to Amazon Aurora MySQL. The migration must have minimal downtime and the source database is currently in use. Which approach should the company take?

Accepted Answer

Use AWS DMS with ongoing replication from the source MySQL database to Aurora.. AWS DMS with ongoing replication (change data capture, CDC) is the correct approach because it allows a live migration with minimal downtime. DMS performs a full load of the 100 GB database and then continuously replicates incremental changes from the source MySQL to the target Aurora MySQL until you cut over, keeping the source fully operational throughout the process.

Answer

Create an Aurora Replica from the on-premises MySQL database and promote it.

Answer

Export the database using mysqldump and import it into Aurora during a maintenance window.

Answer

Take a physical backup of the MySQL database, upload to S3, and restore to Aurora.

Question 11

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.. The correct steps for migrating a 5 TB Oracle database with BFILEs to Amazon RDS for Oracle with minimal downtime are: (B) Use AWS Schema Conversion Tool (SCT) to identify and convert incompatible schema objects, ensuring the target schema is ready. (C) Upload the BFILEs to Amazon S3 and use Oracle Directory objects to reference them in the target database, as BFILEs reference files stored outside the database. (E) Use AWS Database Migration Service (DMS) with the Oracle source endpoint configured to include the BFILE directory path, enabling DMS to migrate the BFILEs during the continuous replication phase, minimizing downtime. Option A (replacing BFILEs with BLOBs) is unnecessary because DMS handles BFILEs natively, and such a change would increase complexity and downtime. Option D (using CloudEndure Migration) is designed for server-level migration, not database-level, and would not be appropriate for this database migration.

Answer

Replace BFILEs with BLOBs in the source database before migration.

Answer

Use AWS CloudEndure Migration to replicate the entire server.

Question 12

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.. Percona XtraBackup creates a physical backup of the MySQL data files, which can be uploaded to Amazon S3 and then restored directly into an Aurora MySQL cluster. This method is significantly faster than logical backups for large databases (200 GB) because it bypasses SQL parsing and row-by-row insertion, making it feasible within a 1-hour downtime window.

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 13

A company is migrating a 3 TB Oracle database to Amazon RDS for Oracle. The migration uses AWS DMS with ongoing replication. The source database is actively used by applications. After the initial full load, the target RDS instance is in sync. However, during the ongoing replication phase, the replication task fails with an error: 'ORA-1555: snapshot too old.' The DMS task has been set up with a source endpoint that uses the 'Oracle TNS' connection method. The company needs to resolve the issue without stopping the source database. Which action should be taken?

Accepted Answer

Increase the undo retention period in the source Oracle database.. The ORA-1555 error indicates that undo data is overwritten before DMS can read it. Increasing undo retention ensures the snapshot data is available longer. Reducing batch size would not address the undo issue. Increasing logging frequency does not affect undo. Using a different connection method does not solve the underlying undo retention problem.

Answer

Change the source endpoint to use the 'Oracle SID' connection method.

Answer

Decrease the batch size of the DMS task.

Answer

Increase the frequency of the DMS task's log mining.

Question 14

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.. RDS for MySQL has a maximum row size limit (65,535 bytes). DMS attempts to insert a row that exceeds this limit. Increasing the instance size does not change the row size limit. Using a different storage engine might help, but InnoDB is default. Enabling compression reduces row size but is not a direct solution for the DMS error.

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 15

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.. DMS full load captures a snapshot of the source database. If the source database has active transactions during the snapshot, some changes may not be included. Using transactional consistency ensures a consistent snapshot. Disabling foreign keys is not recommended. Using a larger instance does not affect consistency.

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.