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

Question 1

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.. Option C is correct. The backup file must be stored with a specific key prefix that includes the AWS account ID and the hyphen, e.g., '123456789012/mybackup.bak'. The error 'Could not find the specified backup file' often occurs when the file is not in the expected path. Option A is wrong because the backup file does not need to be encrypted; native restore can handle unencrypted backups. Option B is wrong because RDS supports native restore from S3; the error is not about unsupported features. Option D is wrong because the backup file extension does not matter; RDS accepts both .bak and .trn files.

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 2

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.. Option C is correct. The 'Memory limit exceeded' error often occurs when DMS cannot keep up with the volume of changes, especially for write-heavy workloads. Increasing the replication instance size provides more memory for buffering. Option A is wrong because stopping and restarting the task does not address the root cause. Option B is wrong because reducing the batch size may not help; the issue is memory capacity. Option D is wrong because enabling multi-AZ does not increase memory; it provides high availability.

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 3

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 4

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.. Using AWS DMS with ongoing replication from an on-premises source to Aurora is the standard approach for near-zero downtime migrations. The other options either require downtime or are not feasible (e.g., Aurora standby cluster cannot be created from on-premises).

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 5

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.. Creating a full backup, transferring to S3, and restoring to RDS is the fastest method with minimal downtime for the given size. DMS requires setting up endpoints and may have overhead. mysqldump is slower for large databases. Read replicas are not applicable for on-premises migration.

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 6

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.. RDS for SQL Server supports TDE using transparent data encryption. The DMS replication can preserve encryption if the target is configured correctly. Option A requires manual certificate management not supported in RDS. Option B uses non-TDE encryption. Option D requires downtime.

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 7

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 SCT is specifically designed to assess and convert database schemas, including stored procedures, to Amazon RDS. DMS focuses on data migration. CloudEndure is for server migration. CodeCommit is for code versioning.

Answer

AWS Database Migration Service (DMS)

Answer

AWS CloudEndure Migration

Answer

AWS CodeCommit

Question 8

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.. Creating an Aurora Replica from a MySQL dump is not possible; Aurora Replicas can only be created from an existing Aurora instance. Using DMS with ongoing replication allows minimal downtime. mysqldump requires downtime. Backup and restore also requires downtime.

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 9

A company is migrating a 1 TB PostgreSQL database from on-premises to Amazon RDS for PostgreSQL. The migration must have minimal downtime. Which TWO steps should be taken to achieve this?

Accepted Answer

Configure AWS DMS with ongoing replication from the source to the target.. DMS with ongoing replication enables minimal downtime by continuously syncing changes. Using pglogical to replicate changes is another approach. Option B (importing a backup) causes downtime. Option D (creating a read replica) is not possible from on-premises. Option E (SCT for schema conversion) may be needed but not for minimal downtime.

Answer

Use AWS SCT to convert the schema to Amazon Aurora.

Answer

Take a full backup using pg_dump and import it into RDS during a maintenance window.

Answer

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

Question 10

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.. DMS can migrate BFILEs if the source endpoint is configured with the directory path. Using SCT to convert any incompatible schema is recommended. Uploading BFILEs to S3 and using Oracle Directory objects with DMS can handle the migration. Option B (direct update) is not secure. Option E (CloudEndure) is for servers.

Answer

Replace BFILEs with BLOBs in the source database before migration.

Answer

Use AWS CloudEndure Migration to replicate the entire server.

Question 11

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.. Using mysqldump with parallel threads can speed up export/import. Percona XtraBackup creates a fast physical backup that can be restored to Aurora. DMS full load may be slower. RDS read replica is not applicable. SCT is for schema conversion.

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 12

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 13

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 14

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.

Question 15

A company is migrating a 2 TB PostgreSQL database from on-premises to Amazon RDS for PostgreSQL. The database has a 4-hour downtime window. The company requires minimal data loss and wants to use AWS DMS. The on-premises network has a 100 Mbps internet connection. Which migration method should the company use?

Accepted Answer

Use AWS DMS with a full load and ongoing change data capture (CDC) replication.. Option B is correct because AWS DMS with a full load and ongoing CDC allows minimal downtime by continuously replicating changes. Option A is wrong because AWS DMS full load only does not capture ongoing changes, leading to data loss. Option C is wrong because pg_dump/pg_restore does not support CDC. Option D is wrong because AWS SCT is a schema conversion tool, not a data migration tool.

Answer

Use AWS Schema Conversion Tool (SCT) to migrate the data to Amazon RDS.

Answer

Use AWS DMS with a full load only, then stop the source database and resume applications.

Answer

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