DBS-C01 Deployment and Migration Practice Test 28 — 15 Questions

Question 1

A company is migrating a 3 TB MySQL database to Amazon Aurora MySQL. They need to validate data consistency after migration. Which approach should they use?

Accepted Answer

Use AWS DMS data validation feature.. AWS DMS data validation feature is the correct approach because it automatically compares source and target records by computing checksums at the table level, ensuring end-to-end consistency without manual intervention. For a 3 TB migration, this built-in feature handles large-scale validation efficiently by validating ongoing replication and full-load data, which is critical for MySQL to Aurora MySQL migrations.

Answer

Compare row counts between source and target tables.

Answer

Run random SELECT queries on a subset of rows to compare values.

Answer

Compute MD5 checksums of the entire dataset in both databases.

Question 2

A company is migrating a MySQL database to Amazon RDS for MySQL. They want to use AWS DMS for continuous replication. Which TWO prerequisites must be met before starting the migration?

Accepted Answer

Enable binary logging (binlog) on the source MySQL database.. Option A is correct because AWS DMS requires binary logging (binlog) to be enabled on the source MySQL database for continuous replication (change data capture); the binlog_format must be set to ROW and the retention period long enough to cover the migration. Option B is correct because the DMS replication instance must have network connectivity to both the source and target databases, typically via VPC security groups, subnets, and routing, otherwise the endpoints cannot be reached and the task will fail. Option C is not required because DMS performs ongoing replication without forcing the source into read-only mode; writes can continue while changes are captured from the binlog. Option D is not a prerequisite because the source database can reside on-premises or outside a VPC, as long as connectivity to the replication instance is established. Option E is not required because DMS logs are written to Amazon CloudWatch Logs, not to an S3 bucket created for migration logs.

Answer

Set the source database to read-only mode during migration.

Answer

Place the source database in a VPC.

Answer

Create an S3 bucket to store the migration logs.

Question 3

A company is migrating a 500 GB Oracle database to Amazon RDS for Oracle. They need to validate the migration and ensure data consistency. Which TWO methods should they use?

Accepted Answer

Use AWS DMS data validation feature.. Option B is correct because AWS Database Migration Service (AWS DMS) includes a built-in data validation feature that compares source and target tables row by row during or after the migration, reporting mismatches and validation failures, which directly supports validating a 500 GB Oracle-to-RDS for Oracle migration. Option D is correct because comparing row counts and checksums (for example, using DBMS_CRYPTO or ORA_HASH on both databases) is a standard, technically sound method to verify data consistency between the source Oracle database and the RDS for Oracle target. Option A is not appropriate because Amazon S3 inventory reports only list objects and metadata in an S3 bucket and cannot validate Oracle database contents. Option C is insufficient because running random SELECT queries on a subset of tables only spot-checks a small portion of data and does not prove full data consistency. Option E is not suitable because CloudWatch Logs captures log output for monitoring and troubleshooting, not for comparing database contents to confirm data consistency.

Answer

Use Amazon S3 inventory reports on the exported data.

Answer

Run random SELECT queries on a subset of tables.

Answer

Use Amazon CloudWatch Logs to compare database logs.

Question 4

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 migrations require a replication instance (D) to run the migration tasks, so a DMS replication instance must be created in the account. You also need a source endpoint (E) that points to the existing PostgreSQL database, which defines the connection and credentials for reading data. Finally, a target endpoint (C) pointing to the Aurora PostgreSQL cluster is required so DMS knows where to load the migrated data. An Application Load Balancer (A) is not part of DMS architecture, and a CloudFormation stack (B) is an optional provisioning method, not a required DMS resource.

Answer

Application Load Balancer for the replication instance.

Answer

AWS CloudFormation stack to provision resources.

Question 5

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 6

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 7

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 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.. 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 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.. Option A is correct because AWS Database Migration Service (DMS) supports ongoing replication (change data capture) from an on-premises PostgreSQL source to an RDS for PostgreSQL target, allowing the bulk load to complete and then continuously applying changes so the cutover downtime is only the short final catch-up. Option C is correct because the pglogical extension provides logical replication between PostgreSQL instances, including from on-premises to RDS for PostgreSQL, so the initial data copy plus continuous streaming of changes keeps the target nearly in sync with minimal downtime. Option B is not appropriate because AWS Schema Conversion Tool is used to convert schemas between different database engines (for example, to Aurora), but this migration is PostgreSQL-to-PostgreSQL, so no engine conversion is needed. Option D would cause significant downtime because a pg_dump taken at cutover and imported into RDS requires the source to be offline for the entire dump and load of a 1 TB database. Option E is not possible because RDS Read Replicas can only be created from an existing RDS or Aurora source, not from an on-premises PostgreSQL database.

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 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 11

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.. AWS DMS with a full load and ongoing change data capture (CDC) replication allows the company to migrate the 2 TB database with minimal data loss within the 4-hour downtime window. The full load transfers the existing data, and CDC captures and applies ongoing changes from the source database to the target RDS instance, reducing the final cutover downtime to seconds or minutes. This approach is ideal for large databases with tight downtime constraints and limited bandwidth (100 Mbps), as the initial full load can run before the downtime window, and only the final CDC catch-up occurs during the window.

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.

Question 12

A company is migrating a 5 TB Oracle database to Amazon RDS for Oracle. The migration must have minimal downtime and support a cutover window of less than 30 minutes. The company is using AWS DMS with ongoing CDC. Which THREE steps should be taken to minimize cutover time? (Choose three.)

Accepted Answer

Configure AWS DMS to use ongoing replication and set the target to apply changes until the source is caught up.. Option A is correct because AWS DMS ongoing replication (CDC) continuously applies source changes to the RDS target, so the target stays nearly synchronized and only a small delta remains at cutover, keeping the switchover within the 30-minute window. Option B is correct because pausing application writes lets CDC drain the remaining change backlog and reach a consistent, caught-up state, which is the essential precondition for a fast, low-downtime cutover. Option C is correct because running AWS DMS data validation confirms the target matches the source before switching over, preventing post-cutover rework or rollback that would blow the downtime budget. Option D is not appropriate because a full backup/restore of a 5 TB database is a bulk, high-downtime operation and is not part of the DMS CDC cutover strategy. Option E is not appropriate because SCT schema conversion is a pre-migration task done before replication starts, not a step that reduces cutover time.

Answer

Take a full backup of the source database and restore it to the target before cutover.

Answer

Use AWS Schema Conversion Tool (SCT) to convert remaining schema objects before cutover.

Question 13

A company is migrating an on-premises MongoDB cluster to Amazon DocumentDB (with MongoDB compatibility). The source cluster uses MongoDB 4.0 and contains 2 TB of data. The company requires minimal downtime during the migration. Which AWS service should be used to perform the migration?

Accepted Answer

AWS Database Migration Service (AWS DMS) with change data capture (CDC). AWS DMS with change data capture (CDC) is the correct choice because it supports MongoDB as a source and Amazon DocumentDB as a target, allowing an initial full load and ongoing replication to keep the target synchronized until cutover. This minimizes downtime and is the standard approach for such migrations. Other methods either lack continuous replication or are not designed for database migration.

Answer

AWS Snowball Edge with AWS DMS

Answer

AWS DataSync

Answer

mongodump and mongorestore utilities

Question 14

A company is deploying a new Amazon Aurora MySQL cluster in a single AWS Region. They require that the cluster be able to survive an Availability Zone (AZ) failure with minimal downtime and no data loss. The application uses the cluster endpoint for writes. Which configuration should they choose?

Accepted Answer

Create an Aurora cluster with one writer instance and one reader instance in different AZs.. Aurora stores data across three AZs and supports rapid failover to a reader instance in a different AZ. By provisioning a writer and a reader in separate AZs, the cluster can automatically promote the reader if the writer's AZ fails, with minimal downtime and no data loss. Other options either do not provide AZ redundancy or are not applicable to Aurora.

Answer

Create an Aurora cluster with one writer instance and one reader instance in the same AZ.

Answer

Create an Aurora cluster with a single writer instance and enable Multi-AZ deployment.

Answer

Create an Aurora cluster with a single writer instance and enable automatic backups.

Question 15

A company is migrating a large on-premises MongoDB database to Amazon DocumentDB. They need to perform the migration with minimal downtime and ensure that the target database is continuously updated during the cutover. Which AWS service should they use?

Accepted Answer

AWS Database Migration Service (AWS DMS) with change data capture (CDC). For minimal downtime migrations, AWS DMS with CDC is the correct choice because it performs an initial full load and then replicates ongoing changes. This keeps the target in sync until cutover. Other options either do not support database replication or lack change capture, making them unsuitable for this scenario.

Answer

AWS Database Migration Service (AWS DMS) with full load only

Answer

AWS DataSync with a scheduled task

Answer

AWS Snowball Edge with a copy of the database files