DBS-C01 Deployment and Migration Practice Test 2 — 15 Questions

Question 1

A company needs to migrate a 100 GB MongoDB database to Amazon DocumentDB (with MongoDB compatibility). The migration must have minimal impact on the source database performance. Which approach should the company take?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Use AWS Database Migration Service (AWS DMS) with ongoing replication from the MongoDB source.. AWS DMS with ongoing replication is the correct approach because it supports continuous change data capture (CDC) from MongoDB, enabling a live migration with minimal performance impact on the source. DMS reads the MongoDB oplog to capture changes without locking the database, which is critical for a 100 GB production database. This allows the target DocumentDB to stay synchronized until cutover, reducing downtime and avoiding the need for a full export/import that would strain the source.

Answer

Use AWS DataSync to transfer the MongoDB data files.

Answer

Set up a MongoDB replica set on Amazon EC2 and promote it to primary, then migrate to DocumentDB.

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Use mongodump to export the data and mongorestore to import into DocumentDB.

Question 2

A company is migrating a 3 TB on-premises Oracle database to Amazon Aurora PostgreSQL using AWS DMS. The migration task is failing with an error indicating insufficient memory. Which TWO actions should the company take to resolve this issue? (Choose TWO.)

Accepted Answer

Increase the instance class of the DMS replication instance.. The 'insufficient memory' error during an AWS DMS migration indicates that the replication instance lacks the memory required to handle the data volume, transformation rules, or cache for large transactions. Increasing the instance class (e.g., from dms.c5.large to dms.c5.2xlarge) provides more memory and CPU, directly resolving the resource constraint.

Answer

Change the target database engine to Amazon RDS for MySQL.

Answer

Disable Multi-AZ on the DMS replication instance.

Answer

Use a smaller instance class for the DMS replication instance.

Question 3

A company is planning to migrate a 1 TB MySQL database from on-premises to Amazon RDS for MySQL. The migration must have minimal downtime and support ongoing replication. Which THREE steps should the company include in the migration plan? (Choose THREE.)

Accepted Answer

Set up an AWS Direct Connect or VPN connection between on-premises and AWS.. A stable, low-latency network connection (Direct Connect or VPN) is essential for AWS DMS to perform ongoing replication with minimal downtime. Without this, the replication can be interrupted by network issues, causing data loss or extended cutover windows.

Answer

Deploy an Amazon EC2 instance to act as a proxy for the DMS replication.

Answer

Install the AWS Schema Conversion Tool on the source server to convert the schema.

Question 4

A team is setting up a DMS migration task. The IAM policy above is attached to the DMS replication instance's IAM role. The team is unable to modify the target RDS instance's maintenance window during the migration. Which additional permission is missing?

Accepted Answer

Add 'rds:ModifyDBInstance' permission for the target RDS instance.. Modifying the target RDS instance's maintenance window requires the `rds:ModifyDBInstance` permission. The DMS replication instance's IAM role must have this permission for the target RDS instance to allow the migration task to adjust the maintenance window, which is necessary to prevent conflicts during ongoing replication. Without this permission, the DMS task cannot alter the maintenance window, even if the IAM role has other RDS permissions.

Answer

Add 'rds:ModifyOptionGroup' permission for the target RDS instance.

Answer

Add 'dms:ModifyReplicationInstance' permission for the DMS replication instance.

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Add 'ec2:DescribeVpcs' permission to the policy.

Question 5

A team is migrating an on-premises database to Amazon RDS using AWS DMS. After the full load completed, the task stopped. The team needs to perform ongoing replication to minimize downtime. What change should the team make to the DMS task?

Accepted Answer

Modify the replication task to change the migration type to 'full-load-and-cdc'.. After a full load completes and the task stops, the team needs to enable ongoing replication to capture and apply changes made to the source database during the migration window. Modifying the DMS task to use the 'full-load-and-cdc' migration type allows the task to perform the initial full load and then seamlessly transition to Change Data Capture (CDC) to replicate incremental changes, minimizing downtime. This is the correct approach because DMS supports switching a completed full-load task to include CDC without re-running the full load.

Answer

Restart the replication task with the same settings.

Answer

Create a new replication instance and start a new full-load task.

Answer

Use AWS Schema Conversion Tool to convert the schema again.

Question 6

A company is migrating a 500 GB on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The migration must have minimal downtime and support ongoing replication after the initial load. Which AWS service should be used?

Accepted Answer

AWS Database Migration Service (DMS) with ongoing replication. AWS Database Migration Service (DMS) with ongoing replication (change data capture, CDC) is required because the scenario demands minimal downtime and continuous synchronization after the initial 500 GB load. DMS uses transaction logs (e.g., PostgreSQL WAL) to capture and apply ongoing changes, enabling a near-zero-duration cutover. Full load only (Option B) would cause downtime during the final sync and cannot support ongoing replication.

Answer

AWS Schema Conversion Tool (SCT)

Answer

AWS Database Migration Service (DMS) with full load only

Answer

AWS Glue

Question 7

A company is migrating a self-managed Oracle database to Amazon Aurora PostgreSQL using AWS DMS. The source database has a large number of tables with foreign key constraints. During the full load phase, some tables fail to load due to foreign key violations. What is the most efficient way to resolve this?

Accepted Answer

Disable foreign key constraints on the target before migration and re-enable after. Disabling foreign key constraints on the target Aurora PostgreSQL database before the migration allows DMS to load tables in any order without violating referential integrity. After the full load completes, re-enabling the constraints ensures data consistency. This approach is the most efficient as it avoids complex dependency ordering and reduces migration failures.

Answer

Increase the DMS task memory and parallel load threads

Answer

Use the table preparation mode 'Do nothing' and load tables in dependency order

Answer

Pre-create all target tables with the same constraints and use 'Truncate' mode

Question 8

A company wants to migrate an on-premises MySQL database to Amazon RDS for MySQL with minimal downtime. They plan to use AWS DMS. Which source database configuration is required to enable ongoing replication (CDC)?

Accepted Answer

Enable binary logging (binlog) on the source database. AWS DMS requires binary logging (binlog) enabled on the source MySQL database to capture ongoing changes for continuous replication (CDC). The binlog records all data modifications (INSERT, UPDATE, DELETE) in a sequential log, which DMS reads to apply those changes to the target RDS instance with minimal downtime. Without binlog enabled, DMS can only perform a full load migration and cannot support ongoing replication.

Answer

Set auto_increment_increment to 1

Answer

Enable the slow query log

Answer

Enable the query cache

Question 9

A company is migrating a 2 TB SQL Server database to Amazon RDS for SQL Server. They need to minimize downtime and are using AWS DMS with CDC. The migration is taking longer than expected during the full load phase. Which change would most likely improve the full load performance?

Accepted Answer

Increase the number of parallel load tasks in the DMS task settings. Increasing the number of parallel load tasks in the DMS task settings allows the full load to be split into multiple concurrent threads, each handling a subset of tables or partitions. This directly improves throughput by utilizing more of the available source and target resources, which is the most effective way to accelerate a slow full load phase when using AWS DMS with CDC.

Answer

Disable CDC to focus on full load only

Answer

Use AWS Schema Conversion Tool to optimize schema

Answer

Use a larger RDS instance class for the target

Question 10

A company is migrating an on-premises MongoDB database to Amazon DocumentDB (with MongoDB compatibility). They want to validate that the data is consistent after migration. Which tool should they use?

Accepted Answer

AWS DMS data validation. AWS DMS data validation is the correct tool because it provides built-in, row-level checksum-based validation that compares source and target data after a full load or ongoing replication. For DocumentDB migrations, DMS can compute and compare checksums on the fly, ensuring consistency without requiring manual scripting or external tools. This is the recommended AWS approach for validating data integrity during and after a migration to DocumentDB.

Answer

mongoexport and mongoimport

Answer

dbHash command on both databases

Answer

DocumentDB native consistency check tool

Question 11

A company is migrating a 1 TB Oracle database to Amazon Aurora PostgreSQL using AWS DMS. They need to ensure minimal downtime and data consistency. Which TWO actions should the company take?

Accepted Answer

Enable change data capture (CDC) on the source Oracle database. Enabling Change Data Capture (CDC) on the source Oracle database allows AWS DMS to capture ongoing changes after the full load, enabling a near-zero downtime migration by continuously replicating transactions to the target Aurora PostgreSQL. Option C is correct because enabling data validation on the DMS task ensures that the data migrated is consistent between the source and target, verifying that no data loss or corruption occurred during the migration process.

Answer

Increase the target Aurora storage to 2 TB to avoid storage issues

Answer

Disable foreign key constraints on the target during migration

Answer

Use AWS Schema Conversion Tool to convert the schema

Question 12

A company is migrating a self-managed PostgreSQL database to Amazon Aurora PostgreSQL. They want to use the pglogical extension for logical replication to minimize downtime. Which THREE prerequisites must be met before setting up pglogical?

Accepted Answer

Add pglogical to shared_preload_libraries and restart the source database. Pglogical must be loaded into the shared preload libraries on the source PostgreSQL instance so that it is available at server start. Without this, the extension cannot be installed or used. The database must be restarted after modifying shared_preload_libraries for the change to take effect.

Answer

Configure max_wal_senders to at least 10

Answer

Enable track_commit_timestamp on the source

Question 13

A company is migrating a 500 GB on-premises PostgreSQL database to Amazon RDS for PostgreSQL. The migration must have minimal downtime and support ongoing replication after the initial load. The network link has limited bandwidth, and the company wants to avoid costly data transfer fees. Which approach should be used?

Accepted Answer

Use AWS DMS with ongoing replication (CDC) from the start.. AWS DMS with ongoing replication (CDC) enables a full load followed by continuous change data capture, which meets the requirements of minimal downtime and ongoing replication. DMS compresses data in transit and can throttle network usage, helping to manage limited bandwidth and avoid costly data transfer fees by using the existing network link efficiently.

Answer

Use AWS Database Migration Service (DMS) with a full load only, then cut over.

Answer

Use pg_dump to export the database and pg_restore to import into RDS.

Answer

Use AWS Snowball Edge to transfer the database files, then load into RDS.

Question 14

A team is using AWS DMS to migrate a 3 TB Oracle database to Amazon Aurora PostgreSQL. They configured the task as shown. After the full load completes, they notice that the target tables have no indexes, primary keys, or foreign keys. What is the most likely cause?

Accepted Answer

The TargetTablePrepMode is set to DROP_AND_CREATE, which creates tables without indexes or constraints.. When TargetTablePrepMode is set to DROP_AND_CREATE, AWS DMS drops the target table if it exists and then creates a new one using only the basic column definitions from the source. It does not migrate indexes, primary keys, or foreign keys because DMS is not designed to replicate schema objects beyond table structure and data. To preserve constraints and indexes, you must either pre-create them on the target or use a different prep mode like TRUNCATE_BEFORE_LOAD.

Answer

The migration task did not include transformation rules to create indexes and constraints.

Answer

The table selection rule uses wildcards and excludes system tables, which also excludes index definitions.

Answer

The task is using a full load without LOB support, which prevents index creation.

Question 15

A company is migrating a 2 TB MySQL database from on-premises to Amazon RDS for MySQL. They need to minimize downtime and ensure data consistency. They plan to use AWS DMS. What is the first step they should take before starting the migration task?

Accepted Answer

Enable binary logging (binlog) on the source MySQL database.. AWS DMS requires binary logging (binlog) to be enabled on the source MySQL database to capture ongoing changes during the full-load and change data capture (CDC) phase. This ensures data consistency and minimizes downtime by allowing DMS to replicate incremental changes after the initial load. Without binlog, DMS cannot perform CDC, and the migration would be limited to a one-time snapshot, risking data loss or extended downtime.

Answer

Create a read replica of the source database to reduce load.

Answer

Disable foreign key checks on the source database to speed up the load.

Answer

Enable binary logging on the target RDS for MySQL instance.