DBS-C01 Practice Test 35 — 15 Questions

Question 1

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. They want to use Oracle GoldenGate for replication. Which AWS service can be used to simplify the setup of GoldenGate on AWS?

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

Accepted Answer

AWS Marketplace. AWS Marketplace offers pre-configured Oracle GoldenGate AMIs that simplify the setup and deployment of GoldenGate on EC2, reducing the manual installation and configuration effort. This is the correct choice because the question asks for a service that simplifies the setup of GoldenGate itself, not the migration tool or infrastructure orchestration.

Answer

AWS DMS

Answer

Amazon RDS for Oracle with GoldenGate enabled

Answer

AWS CloudFormation

Question 2

A company is using Amazon DynamoDB and wants to ensure that only authorized users can access a specific table. Which AWS service should be used to manage access control?

Accepted Answer

AWS Identity and Access Management (IAM).. AWS Identity and Access Management (IAM) is the service used to manage access control for DynamoDB tables by creating policies that grant or deny permissions. Option A (CloudHSM) provides hardware security modules for encryption keys, not access control. Option B (KMS) manages encryption keys but does not handle access control. Option C (VPC security groups) control network traffic at the instance level, not database-level access control.

Answer

AWS CloudHSM.

Answer

AWS Key Management Service (KMS).

Answer

Amazon VPC security groups.

Question 3

A company is designing a highly available e-commerce application using Amazon DynamoDB. The application requires strongly consistent reads for inventory data and eventual consistency for user session data. Which TWO design decisions should the company make?

Accepted Answer

Use strongly consistent reads for the inventory table by setting ConsistentRead=true in the query.. DynamoDB supports strongly consistent reads by setting the `ConsistentRead=true` parameter in the GetItem, Query, or Scan API calls. This ensures that the application always reads the most recent write, which is critical for inventory data where accuracy is paramount. Strongly consistent reads come at the cost of higher latency and lower throughput compared to eventually consistent reads, but they meet the requirement for inventory consistency.

Answer

Enable DynamoDB Streams on the inventory table to replicate data for disaster recovery.

Answer

Use DynamoDB Accelerator (DAX) for the inventory table to provide strongly consistent reads.

Answer

Use a single DynamoDB table for both inventory and session data with different partition keys.

Question 4

A company is using Amazon Aurora MySQL-Compatible Edition. The database is experiencing performance degradation due to long-running queries. The DBA needs to identify the queries that are consuming the most resources. Which action should be taken?

Accepted Answer

Use Amazon RDS Performance Insights to identify the top SQL queries.. Amazon RDS Performance Insights is the correct tool for this scenario because it provides a built-in, easy-to-use dashboard that visualizes database load and identifies the top SQL queries consuming the most resources, such as CPU, I/O, and wait events. Unlike other options, Performance Insights directly correlates database performance metrics with specific queries, enabling the DBA to quickly pinpoint long-running or resource-intensive queries without additional setup or third-party tools.

Answer

Enable Enhanced Monitoring and review the OS process list.

Answer

Enable the slow query log and use a third-party tool to analyze it.

Answer

Enable CloudWatch Logs for the DB instance and search for errors.

Question 5

A company is migrating a 5 TB Oracle database to Amazon Aurora PostgreSQL. They have a 4-hour maintenance window weekly. Which THREE steps should be taken to minimize downtime? (Choose 3)

Accepted Answer

Use AWS Snowball to transfer the initial data load.. AWS Snowball provides a physical data transfer mechanism that avoids saturating the network for the initial 5 TB load, which could otherwise take days over typical internet connections. This allows the bulk data to be loaded into Amazon S3 and then into Aurora PostgreSQL before the cutover, while AWS DMS with CDC (Option D) captures ongoing changes to keep the target synchronized with the source during the migration window. Option E is correct because the AWS Schema Conversion Tool (SCT) is essential for converting the Oracle schema (including data types, stored procedures, and indexes) to Aurora PostgreSQL-compatible format before data migration begins, ensuring compatibility and reducing downtime during the final sync.

Answer

Create an Aurora read replica for testing.

Answer

Use AWS Direct Connect for network connectivity.

Question 6

A company is running an Oracle database on Amazon RDS. The database has a large table that is frequently accessed by multiple applications. The DBA notices that the table has a high number of index scans but the queries are still slow. Upon investigation, the buffer cache hit ratio is low. Which design change would BEST improve performance?

Accepted Answer

Increase the instance size to provide more memory. The low buffer cache hit ratio indicates that the database's memory (buffer cache) is insufficient to cache frequently accessed data blocks, causing excessive physical I/O. Increasing the instance size provides more memory, which expands the buffer cache and allows more data to be cached, reducing disk reads and improving query performance. This directly addresses the root cause of the slow queries despite efficient index scans.

Answer

Convert the table to columnar storage using Amazon Redshift

Answer

Add a read replica to offload queries

Answer

Migrate the table to Amazon DynamoDB with DAX

Question 7

A company is designing a database for an IoT application that collects sensor data every second from millions of devices. The data is time-series and must be stored for 90 days, with occasional queries for recent data. Which AWS database solution is MOST cost-effective and performant?

Accepted Answer

Amazon Timestream. Amazon Timestream is purpose-built for time-series data, offering automatic storage tiering (in-memory for recent data and magnetic for historical data) and serverless scaling, which makes it the most cost-effective and performant choice for ingesting sensor data every second from millions of devices and retaining it for 90 days with occasional queries on recent data.

Answer

Amazon Redshift

Answer

Amazon DynamoDB with TTL to expire old data

Answer

Amazon RDS for MySQL with partitioning

Question 8

A company is deploying a new application that requires a relational database with automatic failover and cross-Region disaster recovery. The application is read-heavy and expects up to 10 GB of data. Which combination of AWS services should be used?

Accepted Answer

Amazon Aurora with Multi-AZ and an Aurora global database. Amazon Aurora with Multi-AZ provides high availability within a single Region, while Aurora Global Database enables cross-Region disaster recovery with typical replication latency of under one second. Aurora is optimized for read-heavy workloads and scales automatically, making it ideal for the 10 GB dataset and the application's requirements.

Answer

Amazon RDS for MySQL with Multi-AZ and a read replica in another Region

Answer

Amazon S3 with AWS Glue and Amazon Athena

Answer

Amazon DynamoDB with global tables

Question 9

A company uses Amazon DynamoDB with AWS KMS-managed encryption at rest. The security team requires that all access to a particular DynamoDB table be logged for audit purposes. Which solution meets this requirement?

Accepted Answer

Enable CloudTrail data events for the DynamoDB table.. AWS CloudTrail logs all DynamoDB API calls, including data plane operations, when data events are enabled. Option A is wrong because VPC Flow Logs capture network traffic, not API calls. Option B is wrong because AWS Config records resource configuration changes, not API calls. Option D is wrong because Amazon GuardDuty is a threat detection service, not a logging service.

Answer

Enable VPC Flow Logs for the VPC where the DynamoDB endpoint is accessed.

Answer

Enable AWS Config rules for DynamoDB.

Answer

Enable Amazon GuardDuty with DynamoDB protection.

Question 10

A company is using Amazon RDS for MySQL and notices that database connections are being rejected intermittently. The application logs show 'Too many connections' errors. The DB instance has 1000 max_connections. Which action should the DBA take to troubleshoot and resolve this issue without impacting performance?

Accepted Answer

Enable Performance Insights and review the 'DB Connections' metric to identify spikes and troubleshoot application connection pooling. Enabling Performance Insights allows the DBA to monitor the 'DB Connections' metric in near real-time, identify exactly when connection spikes occur, and correlate those spikes with application behavior. This diagnostic approach pinpoints the root cause—such as a connection leak or insufficient connection pooling—without making changes that could degrade performance. Increasing max_connections or lowering wait_timeout without understanding the usage pattern can lead to resource exhaustion or premature connection termination.

Answer

Increase the max_connections parameter to 5000 in the DB parameter group

Answer

Create a read replica to offload read traffic

Answer

Set the 'wait_timeout' parameter to a lower value to close idle connections faster

Question 11

A company is migrating a 10 TB Oracle data warehouse to Amazon Redshift. They want to use AWS DMS for continuous replication. However, the migration is taking longer than expected due to LOB columns. What optimization should be applied?

Accepted Answer

Set MaxLobSize to a value like 64 KB to limit inline LOB transfer.. Setting MaxLobSize to a value like 64 KB instructs AWS DMS to treat LOBs smaller than that threshold as inline data, which is transferred more efficiently in the batch stream. This avoids the performance penalty of using FullLobMode, which transfers each LOB individually and can dramatically slow down continuous replication for large tables with many LOB columns.

Answer

Use AWS SCT to compress LOBs.

Answer

Enable FullLobMode to transfer all LOBs.

Answer

Increase the number of DMS tasks.

Question 12

An IAM policy is attached to a user who needs to restore an Amazon RDS DB instance from a DB snapshot. The user attempts to restore and receives an 'Access Denied' error. Which missing permission is MOST likely causing the failure?

Accepted Answer

rds:CreateDBInstance. To restore an Amazon RDS DB instance from a DB snapshot, the user must have the `rds:CreateDBInstance` permission. This is because the restore operation internally calls the CreateDBInstance API to create a new DB instance from the specified snapshot. Without this permission, the request fails with an 'Access Denied' error, even if the user has permissions to describe snapshots or instances.

Answer

rds:DescribeDBSnapshots

Answer

rds:DescribeDBInstances

Answer

rds:CreateDBSubnetGroup

Question 13

A company stores sensitive data in an Amazon RDS for PostgreSQL DB instance. The security team requires that all data at rest be encrypted. The instance is currently unencrypted. What is the simplest way to enable encryption with minimal downtime?

Accepted Answer

Create a snapshot of the DB instance, copy the snapshot with encryption enabled, and restore the snapshot to a new encrypted DB instance.. An existing unencrypted Amazon RDS instance cannot be directly encrypted. The standard approach to enable encryption with minimal downtime is to create a snapshot of the DB instance, copy the snapshot with encryption enabled, and restore the snapshot to a new encrypted DB instance. This process typically involves a brief outage during the restore but is simpler than other methods. Option B is incorrect because the AWS CLI does not support enabling encryption on an existing instance. Option C is incorrect because migrating to RDS Custom adds unnecessary complexity and does not directly enable encryption on the current instance. Option D is incorrect because the AWS Management Console also does not allow enabling encryption on an existing instance.

Answer

Use the AWS CLI to modify the DB instance and enable encryption.

Answer

Migrate the data to an Amazon RDS for PostgreSQL DB instance using RDS Custom.

Answer

Modify the DB instance and enable encryption in the console.

Question 14

Which TWO of the following are benefits of using Amazon RDS Proxy? (Choose TWO.)

Accepted Answer

Reduces the number of database connections by pooling them.. Amazon RDS Proxy acts as a connection broker between your application and the database, maintaining a pool of established connections. When the application opens a new connection, RDS Proxy reuses an idle connection from the pool, which reduces the total number of database connections and prevents the database from being overwhelmed. This pooling mechanism directly addresses the issue of connection exhaustion, especially in serverless or highly concurrent environments.

Answer

Automatically encrypts all traffic between the application and the database.

Answer

Provides built-in read/write splitting for read replicas.

Answer

Reduces storage costs by compressing data in transit.

Question 15

A company is using AWS Database Migration Service (AWS DMS) to migrate a 5 TB MySQL database to Amazon RDS for MySQL. The migration is taking longer than expected. The company notices that the source database has a high volume of write operations. Which configuration change would MOST likely improve the migration performance?

Accepted Answer

Increase the number of parallel threads in the DMS task settings.. Increasing the number of parallel threads in the DMS task settings allows AWS DMS to process multiple table partitions or row changes concurrently, which directly addresses the bottleneck caused by a high volume of write operations on the source. By default, DMS uses a single thread per table, but when the source is under heavy write load, parallel threads can capture and apply changes more efficiently, reducing the overall migration time.

Answer

Enable Multi-AZ on the target RDS instance.

Answer

Use a smaller instance class for the replication instance to reduce cost.

Answer

Set the LOB mode to 'Full LOB mode'.