DBS-C01 Practice Exam 64 — 20 Questions

Question 1

A company's RDS for SQL Server instance is frequently running out of disk space. The instance uses General Purpose SSD (gp2) storage. Which monitoring step will help identify the root cause?

Accepted Answer

Enable Enhanced Monitoring. Enhanced Monitoring provides OS-level metrics such as disk space usage, which can help identify if the instance is running out of disk space due to growth of database files or logs. Option B is incorrect because BinaryLogUsage is a metric specific to MySQL, not SQL Server; RDS for SQL Server uses different metrics like Transaction Log Disk Usage. Options A and C are unrelated to instance disk space.

Answer

Review CloudTrail logs for API calls

Answer

Monitor FreeStorageSpace and BinaryLogUsage metrics

Answer

Monitor BackupStorageUsed metric

Question 2

A database administrator notices that an Amazon RDS for SQL Server DB instance has been in the 'storage-optimization' state for several hours after modifying the storage type from gp2 to io1. What should the administrator do to resolve this?

Accepted Answer

Wait for the storage optimization to complete.. The 'storage-optimization' state is a normal part of the modification process when converting between storage types on RDS. It can take hours as the database migrates to the new storage configuration. The administrator should simply wait for the process to complete. Options B, C, and D are incorrect: restoring from a snapshot would lose recent changes and requires reapplication of the modification, modifying back to gp2 would interrupt the process and still require time, and rebooting does not affect the storage optimization.

Answer

Restore from the latest snapshot and reapply the modification.

Answer

Cancel the modification by modifying the DB instance back to gp2.

Answer

Reboot the DB instance.

Question 3

Which THREE are factors to consider when choosing between Amazon RDS and Amazon DynamoDB? (Select THREE.)

Accepted Answer

Serverless capacity management. Amazon RDS requires manual or auto-scaling of compute and storage capacity, while DynamoDB offers serverless capacity management with on-demand mode that automatically scales throughput based on traffic. This is a key differentiator when deciding between provisioned capacity (RDS) and fully managed, pay-per-request scaling (DynamoDB).

Answer

Encryption at rest requirements

Answer

Need for in-memory caching

Question 4

A company is running a self-managed MongoDB cluster on Amazon EC2. The cluster consists of three replica set members in different Availability Zones. The primary node recently experienced a crash, and the cluster failed over to a secondary. However, the new primary is showing significantly higher latency. The operations team wants to ensure that failover is fast and consistent. What should be done to improve the failover reliability?

Accepted Answer

Use Amazon EBS io2 Block Express volumes with provisioned IOPS.. Amazon EBS io2 Block Express volumes provide high IOPS and low latency, which can significantly reduce the time required for a secondary node to catch up and become the new primary after a failover. This improves failover reliability and reduces latency spikes. Option B is incorrect: EBS Multi-Attach is designed for shared block storage across multiple instances and is not suitable for MongoDB replica sets; using it could lead to data corruption. Option C is incorrect: while instance store volumes offer high I/O performance, they are ephemeral; if the instance fails, data is lost, making them unreliable for database workloads. Option D is incorrect: EBS snapshots are for backup and disaster recovery, not for improving failover performance.

Answer

Use Amazon EBS Multi-Attach to allow all replicas to share the same volume.

Answer

Switch to instance store volumes for better I/O performance.

Answer

Configure EBS snapshots to be taken every 5 minutes.

Question 5

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. Which TWO methods can the database specialist use to minimize downtime during the migration?

Accepted Answer

Use Oracle GoldenGate to replicate data continuously.. Oracle GoldenGate enables continuous, real-time data replication from the source Oracle database to Amazon RDS for Oracle, allowing the source to remain fully operational during the migration. When the cutover is performed, only a brief pause is needed to apply any final transactions, minimizing downtime to seconds or minutes.

Answer

Use Oracle Recovery Manager (RMAN) to back up and restore.

Answer

Take a full database backup and restore to RDS.

Answer

Use Oracle Data Pump to export and import the database.

Question 6

A company is using Amazon Aurora MySQL-Compatible Edition. The security team wants to restrict access to the database so that only specific applications running on Amazon EC2 instances can connect. The EC2 instances are in the same VPC as the Aurora cluster. Which combination of steps should be taken to enforce this restriction?

Accepted Answer

Configure the Aurora cluster's security group to allow inbound traffic from the EC2 instances' security group.. Configuring the Aurora cluster's security group to allow inbound traffic from the EC2 instances' security group is the correct approach because security groups can reference other security groups as a source, enabling dynamic, instance-level access control without managing individual IP addresses. Option A is incorrect because IAM database authentication manages user authentication at the database level, not network access. Option B is incorrect because the DB subnet group defines the subnets where the Aurora cluster can be placed, not traffic filtering rules. Option C is incorrect because network ACLs are stateless and operate at the subnet boundary, making them less granular and harder to manage for instance-specific access compared to security group references.

Answer

Enable IAM database authentication and create database users for each application.

Answer

Modify the DB subnet group to include only subnets where the EC2 instances reside.

Answer

Use a network ACL to allow traffic only from the EC2 instances' IP addresses.

Question 7

A developer is trying to connect to an RDS for PostgreSQL instance using the endpoint shown in the exhibit. The connection fails with a timeout. Which of the following is the most likely cause?

Accepted Answer

The security group does not allow inbound traffic on port 5432 from the client IP.. The most likely cause is that the security group does not allow inbound traffic on port 5432 from the client IP, causing a timeout. Option A is incorrect because the endpoint is correctly provided by AWS; an incorrect endpoint would produce a different error. Option B is incorrect because SSL encryption is not required by default; if it were, the error would be an SSL handshake failure, not a timeout. Option D is incorrect because Multi-AZ configurations use the same endpoint; no separate endpoint is needed.

Answer

The endpoint address is incorrect.

Answer

The DB instance requires SSL encryption to connect.

Answer

The DB instance is in a Multi-AZ configuration and requires a different endpoint.

Question 8

A company is running an Amazon DynamoDB table with on-demand capacity. The application is experiencing high latency for GetItem operations. CloudWatch shows that 'ThrottledRequests' is zero, but 'ConsumedReadCapacityUnits' is consistently below the provisioned limit. The table has a global secondary index (GSI) with a different partition key. What is the most likely cause of the high latency?

Accepted Answer

Throttling on the base table due to hot partitions. While throttling on a Global Secondary Index (GSI) can cause backpressure and affect writes to the base table, it does not directly impact read operations like GetItem. In this scenario, with zero ThrottledRequests, throttling is not occurring on the base table or GSI. The high latency is more likely caused by a hot partition on the base table, which can still result in increased response times even before throttling metrics are triggered. Option C is therefore incorrect; the correct answer is D.

Answer

High write activity on the base table causing read latency

Answer

Insufficient provisioned read capacity on the base table

Answer

Throttling on the global secondary index due to uneven access patterns

Question 9

A company is using an Amazon Aurora MySQL DB cluster. The company wants to implement a backup strategy that supports point-in-time recovery (PITR) with a recovery time objective (RTO) of 15 minutes and a recovery point objective (RPO) of 5 minutes. Which TWO actions should the company take?

Accepted Answer

Configure automated backups with a retention period of at least 1 day.. Aurora automated backups with a retention period of at least 1 day provide continuous backup and point-in-time recovery (PITR) with an RPO of 5 minutes because transaction logs are uploaded every 5 minutes. This meets the required RPO of 5 minutes, and restoring can achieve an RTO under 15 minutes. Option E is correct because Aurora Backtrack allows rewinding the cluster to a specific point in time, achieving an RPO of 5 minutes and an RTO of minutes (typically under 15). No other option meets both the stated RTO and RPO.

Answer

Create manual snapshots every 5 minutes.

Answer

Enable cross-Region replication for the cluster.

Answer

Enable parallel query for the cluster.

Question 10

A company's security policy requires that all database passwords be rotated every 90 days. The company uses AWS Secrets Manager to store database credentials for Amazon RDS. Which feature can be used to automate password rotation?

Accepted Answer

Configure automatic rotation in Secrets Manager with a rotation interval of 90 days.. Secrets Manager has built-in rotation support for RDS databases. Option B is wrong because Lambda can be used but is not a feature of Secrets Manager itself; the managed rotation is the simplest. Option C is wrong because IAM Access Analyzer is for analyzing resource policies, not password rotation. Option D is wrong because Systems Manager Parameter Store does not have built-in rotation for RDS.

Answer

Use an AWS Lambda function triggered by Amazon CloudWatch Events every 90 days to rotate the password.

Answer

Use IAM Access Analyzer to detect unused passwords and rotate them.

Answer

Store the password in AWS Systems Manager Parameter Store and use automatic rotation.

Question 11

A company is monitoring an Amazon RDS for Oracle instance. CloudWatch alarms show that FreeableMemory is consistently below 256 MB. The database has high read and write I/O. Which THREE steps should the database specialist take to diagnose the issue?

Accepted Answer

Check the MemoryPressure and LogFileSyncDuration metrics in CloudWatch.. Options A, B, and E are correct diagnostic steps. A: Checking MemoryPressure and LogFileSyncDuration helps identify memory pressure and I/O bottlenecks. B: Reviewing V$MEMORY_TARGET_ADVICE provides Oracle's memory sizing recommendations. E: Querying V$SGASTAT and V$PGASTAT reveals detailed memory allocation within SGA and PGA. Option C (enabling storage auto scaling) addresses storage, not memory. Option D (increasing instance class) is a remediation step, not a diagnostic step.

Answer

Enable storage auto scaling to increase allocated storage.

Answer

Increase the DB instance class to allocate more memory.

Question 12

A company is migrating a 500 GB MySQL database to Amazon Aurora MySQL. The migration must have minimal downtime and the source database is already using binary logging. Which migration approach should be used?

Accepted Answer

Set up binary log replication from the source to an Aurora MySQL cluster. MySQL native binary log replication can be set up directly from a source MySQL database to an Amazon Aurora MySQL cluster. Since binary logging is already enabled, the Aurora cluster can act as a replica, synchronizing continuously with minimal downtime. This approach allows a full load followed by ongoing replication, meeting the requirement for near-zero downtime migration.

Answer

Take a snapshot of the source database and restore to Aurora

Answer

Use AWS DMS with full load only

Answer

Use mysqldump to export the data and import into Aurora

Question 13

A company's Amazon RDS for PostgreSQL instance is experiencing a high number of connections, causing performance degradation. The DBA wants to identify which user and application are creating the most connections. What should the DBA do?

Accepted Answer

Enable Performance Insights and use the 'db.sql_tokenized' dimension to analyze connections by user.. Performance Insights with the 'db.sql_tokenized' dimension allows database administrators to group and analyze database connections by user and application, helping identify the source of high connection counts. Option A (CloudTrail) logs API calls, not database-level logins. Option C (Enhanced Monitoring) provides OS-level metrics like connection count but does not break down by user or application. Option D (VPC Flow Logs) captures network traffic metadata, not database connection details.

Answer

Enable AWS CloudTrail to log database logins.

Answer

Enable Enhanced Monitoring and check the 'Connection Count' metric.

Answer

Enable VPC Flow Logs to track connection attempts.

Question 14

A company is using Amazon Redshift for data warehousing. The users report that queries are slow, and the CloudWatch metric 'CPUUtilization' shows high usage. The cluster has 4 dc2.large nodes. The administrator runs the following query: SELECT * FROM stl_query WHERE starttime > '2023-12-01' ORDER BY duration DESC LIMIT 10; This shows that the longest query runs for over 5 minutes. Which of the following is the MOST effective way to improve query performance?

Accepted Answer

Add more nodes to the cluster (scale out). Adding more nodes to the cluster (scale out) distributes the workload across additional compute resources, increasing parallelism and CPU capacity. This directly addresses the high CPU utilization and reduces query execution time. Option A is incorrect because the issue is CPU, not storage; increasing storage volume does not improve CPU performance. Option C is incorrect: VACUUM reclaims disk space and sorts data but does not directly improve query performance when the bottleneck is CPU. Option D is incorrect: increasing WLM concurrency allows more queries to run simultaneously but may actually increase contention and not improve the performance of individual long-running queries.

Answer

Increase the size of the cluster volume by adding more storage

Answer

Run the VACUUM command to reclaim space and improve query performance

Answer

Modify the workload management (WLM) queue to increase concurrency

Question 15

A database specialist is troubleshooting a performance issue on a self-managed PostgreSQL database that they plan to migrate to Amazon RDS. The database has a high number of 'idle in transaction' connections. What is the impact of these connections on the database?

Accepted Answer

They hold locks and prevent cleanup of dead tuples, leading to bloat.. Idle-in-transaction connections hold locks and prevent PostgreSQL's autovacuum from cleaning up dead tuples, leading to table bloat and performance degradation. Option A is wrong because idle transactions do not cause constant polling; CPU usage remains low. Option C is wrong because they do not prevent new connections from being established unless the max_connections limit is reached. Option D is wrong because idle transactions do not significantly increase write-ahead logging.

Answer

They increase CPU usage due to constant polling.

Answer

They prevent new connections from being established.

Answer

They cause increased disk I/O from write-ahead logging.

Question 16

A company is designing a document database on Amazon DocumentDB. The workload requires high write throughput and needs to support complex queries on nested attributes. Which THREE design considerations should the company evaluate to meet these requirements?

Accepted Answer

Denormalize data to reduce the number of joins.. Denormalizing data in Amazon DocumentDB reduces the need for joins, which are expensive and can degrade write throughput. By embedding related data into a single document, the database can perform complex queries on nested attributes more efficiently, as DocumentDB is optimized for document-level operations. This design aligns with the workload's requirement for high write throughput and complex query support.

Answer

Enable Multi-AZ deployment for high availability.

Answer

Use change streams to capture and process data changes.

Question 17

A company is migrating a 500 GB database from Amazon RDS for MySQL to Amazon Aurora MySQL. The migration must be completed with minimal downtime and no data loss. The RDS instance is Multi-AZ. Which approach should be used?

Accepted Answer

Create an Aurora MySQL read replica from the RDS MySQL instance, then promote it. Creating an Aurora MySQL read replica from the RDS MySQL instance uses the native MySQL binary log (binlog) replication to keep the Aurora cluster synchronized with minimal downtime. Once the replica lag reaches zero, you promote the Aurora cluster to make it the primary database, ensuring no data loss and a very short cutover window.

Answer

Use AWS DMS with ongoing replication from RDS to Aurora

Answer

Take a snapshot of the RDS instance and restore to Aurora

Answer

Set up native MySQL replication from the RDS Multi-AZ standby to Aurora

Question 18

A company is using Amazon Redshift for data warehousing. The database administrator needs to identify which queries are consuming the most resources. Which system view should be queried?

Accepted Answer

STV_RECENTS. The STV_RECENTS system view in Amazon Redshift provides a list of currently running and recently completed queries, including their process IDs, user names, and execution status. This makes it the correct choice for identifying which queries are consuming the most resources at the moment, as it directly reflects active and recent workload.

Answer

SVV_TABLES

Answer

STL_LOAD_ERRORS

Answer

STL_DDLTEXT

Question 19

A company is using Amazon DynamoDB for a gaming leaderboard application. Recently, users have experienced increased latency when updating scores. The DynamoDB table has on-demand capacity mode. The application performs UpdateItem calls with a condition expression. Which action is most likely to reduce the latency?

Accepted Answer

Ensure that there are no throttled requests in the CloudWatch metrics and verify that the table is not experiencing hot partitions.. Increased latency in DynamoDB can be caused by hot partitions where many requests hit the same partition, leading to throttling even with on-demand capacity if the partition limits are exceeded. Checking CloudWatch metrics for throttled requests and partition metrics helps identify hot partitions. Option A is incorrect because adding a GSI does not improve UpdateItem performance; it only helps query performance. Option B is incorrect: on-demand mode already handles capacity, and increasing read capacity units does not affect write operations like UpdateItem. Option C is incorrect: disabling conditional writes would break the application's concurrency control and does not guarantee latency reduction; condition evaluation is a fast, internal operation.

Answer

Add a global secondary index (GSI) with the score as the sort key to improve update performance.

Answer

Switch the table to provisioned capacity and increase the read capacity units to handle peak load.

Answer

Disable conditional writes to reduce the overhead of condition expression evaluation.

Question 20

Refer to the exhibit. A database administrator retrieves CloudWatch metrics for an RDS instance. What is the trend of CPU utilization during the monitored period?

Accepted Answer

CPU utilization is increasing over time.. The average CPU utilization increases from 75.5% to 98.2% over the hour, indicating a steady increase. Option A is incorrect because it is not decreasing. Option B is incorrect because it is not constant around 90%. Option C is incorrect because it does not fluctuate randomly; it increases monotonically.

Answer

CPU utilization is decreasing over time.

Answer

CPU utilization is constant around 90%.

Answer

CPU utilization fluctuates randomly.