DBS-C01 Deployment and Migration Practice Test 13 — 15 Questions

Question 1

An administrator runs the CLI command shown in the exhibit and sees the output. The DB instance 'mydb' is currently running MySQL 5.7.22. What does the output indicate?

Accepted Answer

The DB instance has a pending minor version upgrade to 5.7.23. The output shows 'Pending maintenance: Yes' with 'Minor version upgrade to 5.7.23' listed. This indicates that the DB instance has a pending minor version upgrade that will be applied during the next maintenance window. The CLI command 'aws rds describe-db-instances --db-instance-identifier mydb' returns this information when a minor version upgrade is scheduled but not yet applied.

Answer

The master user password has been changed

Answer

The DB instance has failed to apply modifications

Answer

The DB instance is using a custom DB parameter group

Question 2

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 3

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 4

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 5

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.. Increasing the replication instance size to dms.c5.2xlarge provides more CPU and memory, which can handle higher transaction throughput, reducing CDC lag. Option B is wrong because enabling Multi-AZ on a replication instance does not directly improve performance; it adds redundancy and can even introduce latency. Option C is wrong because splitting the migration into multiple tasks for a single source database adds overhead and may cause conflicts, and it does not necessarily reduce lag. Option D is wrong because disabling ongoing replication would result in data loss and does not meet the minimal downtime requirement.

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 6

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.. Using a DMS full load with ongoing replication minimizes downtime and works within the network constraints. Option A is wrong because taking a dump over the network would take too long. Option C is wrong because using Snowball is overkill for 200 GB and shipping would take too long. Option D is wrong because using a larger instance is unnecessary and costly.

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 7

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 8

A company is migrating a 3 TB Oracle database from on-premises to Amazon RDS for Oracle. The migration must have zero downtime. The on-premises server uses Oracle Data Guard for disaster recovery. The network bandwidth is 200 Mbps. The team plans to use AWS DMS with CDC from Oracle redo logs. During the initial full load, DMS reports that the source table 'ORDERS' has a table-level supplemental log missing. The migration fails. What should the team do first to resolve this issue?

Accepted Answer

Enable supplemental logging on the Oracle source database for the 'ORDERS' table.. AWS DMS requires supplemental logging on the source Oracle tables to capture change data for CDC. Without it, DMS cannot track changes. Option A is incorrect because switching to Oracle GoldenGate would not address the root cause and adds complexity. Option B is incorrect because using AWS SCT and native export/import does not provide zero-downtime migration. Option D is incorrect because recreating the task with 'full load only' would lose the CDC requirement, causing downtime for ongoing changes.

Answer

Switch to Oracle GoldenGate for migration.

Answer

Use AWS SCT to convert the schema and then use a native export/import.

Answer

Recreate the DMS task with 'full load only' to bypass CDC.

Question 9

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.. The replication lag is increasing because the RDS instance is not powerful enough to apply changes from the write-heavy source as fast as they arrive. Increasing the RDS instance class (option C) provides more CPU and memory resources, allowing the replica to apply transactions more quickly and reduce lag. Option A (tuning the source) might help but is not the most direct solution if the target is the bottleneck. Option B (Multi-AZ) improves availability, not replication performance. Option D (AWS DMS) is an alternative migration tool but does not directly address lag in an existing native replication setup.

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 10

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.

Question 11

A company is migrating a 2 TB Oracle database to Amazon RDS for Oracle. The migration requires minimal downtime. They use AWS SCT to convert the schema and AWS DMS for data migration. After the full load, DMS ongoing replication is unable to capture changes because the archived redo logs are being deleted on the source before DMS can read them. The source database has a log retention setting of 2 hours. The team cannot increase the retention due to storage constraints. What should they do?

Accepted Answer

Configure DMS to use an S3 bucket to store archived redo logs.. AWS DMS supports storing archived redo logs in an S3 bucket as a staging area, which allows DMS to process the logs before they are deleted from the source. This resolves the issue without requiring increased log retention on the source. Option A (full load only) would cause downtime. Option B (disabling archiving) would prevent DMS from capturing ongoing changes. Option C (increasing DMS instance size) does not affect log reading speed from archived logs.

Answer

Switch to a full load only migration strategy.

Answer

Disable archiving on the source database.

Answer

Increase the DMS replication instance size to improve log reading speed.

Question 12

A company has a 50 GB MariaDB database on an on-premises server. They want to migrate to Amazon RDS for MariaDB. They have a 100 Mbps network connection. The migration window is 2 hours. The database can be offline for up to 30 minutes. Which migration approach is most appropriate?

Accepted Answer

Create a MariaDB dump, transfer to an EC2 instance in the same region, then import to RDS.. The most appropriate because a MariaDB dump to an EC2 instance in the same region allows for a fast transfer over the network, and the import into RDS can be completed within the 2-hour migration window. The 50 GB database at 100 Mbps can be transferred in just over an hour, well within the window. Option A (DMS with ongoing replication) is unnecessarily complex for a one-time migration and may require more setup time. Option B (Snowball) is overkill for 50 GB and would not meet the 2-hour window due to shipping and processing delays. Option D (SCT) is not needed since the source and target are both MariaDB, and schema conversion is unnecessary.

Answer

Use AWS DMS with ongoing replication.

Answer

Use AWS Snowball to transfer the database files.

Answer

Use AWS SCT to convert schema and then use DMS.

Question 13

A company wants to migrate a 1 TB MySQL database to Amazon Aurora MySQL with minimal downtime. The database has a high write load. Which TWO options are valid approaches? (Choose two.)

Accepted Answer

Use AWS DMS with full load and ongoing replication.. AWS DMS supports full load and ongoing change data capture (CDC) replication, which can migrate the 1 TB MySQL database to Aurora MySQL with minimal downtime by continuously applying changes from the source binary logs. This approach handles high write loads efficiently by using transactional replication to keep the target nearly synchronized until cutover.

Answer

Export to flat files, transfer via AWS Snowball, and import.

Answer

Perform a mysqldump and restore to Aurora.

Answer

Use AWS SCT to convert the schema and then use DMS.

Question 14

A company is migrating a 500 GB MySQL database from on-premises to Amazon RDS for MySQL. The database is critical and must have minimal downtime. Which approach should be used to migrate the database with the least downtime?

Accepted Answer

Use AWS Database Migration Service (DMS) with a replication instance to perform a full load and then ongoing replication until cutover.. AWS DMS with ongoing replication (change data capture) is the correct approach because it performs an initial full load of the 500 GB database and then continuously replicates incremental changes from the source to the target RDS instance. This allows the source database to remain operational during migration, and the cutover can be performed in seconds by stopping application writes and applying the final changes, minimizing downtime to near zero.

Answer

Modify the on-premises database to use a new master user and then use the AWS Schema Conversion Tool to migrate.

Answer

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

Answer

Export the database using mysqldump and import into RDS using mysql command-line tool. Schedule a maintenance window for cutover.

Question 15

A financial services company is migrating a 2 TB Oracle database to Amazon Aurora PostgreSQL. The database uses Oracle-specific features like hierarchical queries and stored procedures. The company wants to minimize manual code changes. Which service should be used to automate schema conversion?

Accepted Answer

AWS Schema Conversion Tool (SCT).. AWS Schema Conversion Tool (SCT) is specifically designed to convert database schemas from one engine to another, including Oracle to Amazon Aurora PostgreSQL. It automates the conversion of Oracle-specific features like hierarchical queries (CONNECT BY) and stored procedures into PostgreSQL-compatible syntax (e.g., recursive CTEs and PL/pgSQL), minimizing manual code changes. This makes SCT the correct choice for schema conversion, while AWS DMS handles data migration separately.

Answer

AWS Database Migration Service (DMS) with full load and ongoing replication.

Answer

AWS Storage Gateway to cache data on-premises and then sync to S3.

Answer

AWS Lambda to execute custom scripts for schema transformation.