DBS-C01 Monitoring and Troubleshooting Practice Test 15 — 15 Questions

Question 1

A company runs an Amazon RDS for Oracle DB instance. The database administrator wants to receive an alert when the storage space is below 10% of the allocated storage. Which Amazon CloudWatch metric and alarm threshold should be used?

Accepted Answer

Metric: FreeStorageSpace, Condition: < 10% of 100 GB (10 GB). The metric FreeStorageSpace shows the available storage in bytes. The alarm should be set to when FreeStorageSpace is less than 10% of allocated storage. Option B is correct. Option A is wrong because it's a percentage of total. Option C is wrong because it's a fixed value. Option D is wrong because BinaryLog usage is not relevant.

Answer

Metric: BinaryLogUsage, Condition: > 10%

Answer

Metric: FreeableMemory, Condition: < 10% of total memory

Answer

Metric: DiskQueueDepth, Condition: > 10

Question 2

A company uses Amazon DynamoDB with a table that has a partition key of 'user_id' (string) and sort key of 'timestamp' (number). The application queries for recent items for a specific user using the query API with KeyConditionExpression. The query returns items in descending order. Occasionally, the query returns items that are not the most recent. What is the most likely cause?

Accepted Answer

The query is using eventually consistent reads, which may not reflect the latest writes.. DynamoDB stores items with the same partition key in sorted order by sort key. Queries return items in order by default. Option C is correct because if the application uses eventually consistent reads, the data might be stale. Option A is wrong because GSIs don't affect base table queries. Option B is wrong because the query returns items in order, but eventually consistent reads may not reflect latest writes. Option D is wrong because pagination is not the cause.

Answer

The query is not using the ScanIndexForward parameter set to false.

Answer

The query results are paginated and the application is not iterating through all pages.

Answer

The query is using a global secondary index (GSI) that has a different sort key.

Question 3

A company is troubleshooting an Amazon RDS for MySQL DB instance that is experiencing high CPU utilization. The DB instance is a db.t3.medium. Which TWO actions should the database administrator take to investigate the cause?

Accepted Answer

Enable Performance Insights to identify the top SQL queries consuming CPU.. Option A is correct because enabling Performance Insights helps identify top SQL queries. Option B is correct because reviewing slow query logs helps identify inefficient queries. Option C is wrong because increasing instance size is a fix, not investigation. Option D is wrong because disabling Multi-AZ reduces availability, not CPU. Option E is wrong because modifying parameter groups without analysis is not investigative.

Answer

Disable Multi-AZ to reduce overhead.

Answer

Modify the DB parameter group to increase the query cache size.

Answer

Increase the DB instance class to a larger size.

Question 4

A company is using Amazon DynamoDB with auto scaling enabled. The table has a provisioned read capacity of 10,000 RCU and write capacity of 5,000 WCU. Auto scaling target utilization is 70%. The table experiences a sudden spike in read traffic, reaching 12,000 RCU. The table throttles some requests. Which THREE actions should the company take to prevent future throttling?

Accepted Answer

Implement exponential backoff in the application to retry throttled requests.. Option A is correct because increasing the maximum read capacity prevents throttling. Option B is correct because enabling DynamoDB Accelerator (DAX) reduces read load. Option E is correct because implementing exponential backoff helps handle throttling gracefully. Option C is wrong because decreasing target utilization would cause auto scaling to scale out earlier, but it would not prevent throttling during spikes because auto scaling reacts after the spike. Option D is wrong because write capacity is not the issue.

Answer

Decrease the auto scaling target utilization to 50% to scale out earlier.

Answer

Increase the write capacity to 10,000 WCU.

Question 5

A database administrator is monitoring an Amazon RDS for PostgreSQL DB instance. The administrator notices that the DB instance is using more memory than expected. Which TWO metrics in Amazon CloudWatch can help diagnose memory usage?

Accepted Answer

FreeableMemory. Option A is correct because FreeableMemory shows available memory. Option D is correct because SwapUsage indicates swapping, which occurs when memory is low. Option B is wrong because ReadIOPS is I/O metric. Option C is wrong because DatabaseConnections shows connections, not memory. Option E is wrong because NetworkReceiveThroughput is network metric.

Answer

NetworkReceiveThroughput

Answer

ReadIOPS

Answer

DatabaseConnections

Question 6

A company is using Amazon RDS for MySQL with Multi-AZ deployment. The application team reports increased latency during peak hours. Which AWS service should the database specialist use to identify the root cause?

Accepted Answer

Enable Performance Insights for the RDS instance and analyze the database load.. Option B is correct because Performance Insights provides database performance metrics and helps identify bottlenecks. Option A is wrong because CloudWatch Metrics Dashboard shows aggregated metrics but does not provide detailed database performance analysis. Option C is wrong because AWS Config is for resource configuration auditing. Option D is wrong because Amazon Inspector is for security assessments.

Answer

Enable AWS Config to track configuration changes to the RDS instance.

Answer

Use the CloudWatch Metrics Dashboard to analyze database connections.

Answer

Run an Amazon Inspector assessment on the RDS instance.

Question 7

A database specialist is troubleshooting an Amazon RDS for PostgreSQL instance that is experiencing intermittent connection timeouts. The application logs show errors like 'FATAL: remaining connection slots are reserved for non-replication superuser connections'. The max_connections parameter is set to 100. What should the specialist do to resolve this issue?

Accepted Answer

Modify the 'max_connections' parameter to a higher value and reboot the instance.. Option C is correct because the error indicates connection pool exhaustion. Increasing max_connections allows more concurrent connections. Option A is wrong because the error is about connection slots, not idle sessions. Option B is wrong because reserving more slots for superusers does not address the root cause. Option D is wrong because the error is not due to replication slots.

Answer

Increase the 'max_replication_slots' parameter to allow more replication connections.

Answer

Increase the value of the 'superuser_reserved_connections' parameter.

Answer

Enable RDS Proxy to manage database connections efficiently.

Question 8

A company is running a production Amazon DynamoDB table and notices that read requests are being throttled. The table has on-demand capacity mode enabled. Which action should the database specialist take to troubleshoot the throttling?

Accepted Answer

Check the CloudWatch metric 'ThrottledRequests' for the table and review 'SystemErrors' to identify hot partitions.. Option A is correct because throttling with on-demand capacity can be due to a single partition receiving too many requests. Option B is wrong because switching to provisioned capacity does not fix the root cause. Option C is wrong because CloudWatch does not have a metric for hot partitions. Option D is wrong because enabling auto scaling is for provisioned capacity.

Answer

Enable auto scaling on the table to automatically adjust capacity.

Answer

Enable DynamoDB Accelerator (DAX) to reduce read load on the table.

Answer

Switch the table to provisioned capacity mode and increase the read capacity units.

Question 9

A database specialist is troubleshooting an Amazon RDS for SQL Server instance that is running out of storage. The instance has 500 GB of provisioned storage and is using General Purpose SSD (gp2). The specialist wants to set up an alarm to notify when free storage space drops below 50 GB. Which CloudWatch metric and threshold should be used?

Accepted Answer

Monitor the 'FreeStorageSpace' metric in bytes and set a threshold of 53687091200.. Option B is correct because 'FreeStorageSpace' metric in bytes should be monitored. 50 GB = 50 * 1024^3 bytes = 53687091200 bytes. Option A is wrong because 'FreeStorageSpace' in bytes is the correct metric. Option C is wrong because 'FreeStorageSpace' is in bytes, not percent. Option D is wrong because 'FreeStorageSpace' is the correct metric.

Answer

Monitor the 'FreeStorageSpace' metric in percent and set a threshold of 10.

Answer

Monitor the 'DiskSpaceUtilization' metric and set a threshold of 90.

Answer

Monitor the 'FreeStorageSpace' metric in gigabytes and set a threshold of 50.

Question 10

A company is using Amazon ElastiCache for Redis to cache frequently accessed data. Recently, the application has been experiencing increased latency. The database specialist suspects that the cache hit ratio has decreased. Which CloudWatch metric should the specialist analyze to confirm this suspicion?

Accepted Answer

Monitor 'CacheHits' and 'CacheMisses' metrics to calculate the hit ratio.. Option A is correct because the cache hit ratio is calculated as CacheHits / (CacheHits + CacheMisses). Option B is wrong because CurrConnections shows current connections. Option C is wrong because Evictions shows number of evicted keys. Option D is wrong because ReplicationLag shows replication delay.

Answer

Monitor the 'CurrConnections' metric to see if there are too many connections.

Answer

Monitor the 'Evictions' metric to see if keys are being evicted.

Answer

Monitor the 'ReplicationLag' metric to check replication delay.

Question 11

A database specialist is trying to connect to an Amazon RDS for MySQL instance from an EC2 instance but receives a 'Connection timed out' error. The security group for the RDS instance allows inbound traffic on port 3306 from the security group of the EC2 instance. What should the specialist check next?

Accepted Answer

Check the network ACL associated with the subnet of the RDS instance to ensure it allows inbound traffic on port 3306 and outbound traffic on ephemeral ports.. Option D is correct because the network ACL must allow inbound traffic on ephemeral ports for the response. Option A is wrong because the security group already allows inbound on 3306. Option B is wrong because the error is 'Connection timed out', not authentication. Option C is wrong because if the VPC had no internet gateway, the error would be different for private connections.

Answer

Check that the RDS instance has a public DNS name and the EC2 instance can resolve it.

Answer

Ensure that the VPC has an internet gateway attached and the route table has a route to it.

Answer

Verify that the security group for the EC2 instance allows outbound traffic on port 3306.

Question 12

A company is running an Amazon Aurora MySQL database cluster. The database specialist notices that the write latency is high during peak hours. The cluster consists of one writer and two reader instances. Which action should the specialist take to reduce write latency?

Accepted Answer

Increase the instance class of the writer instance to a larger size.. Option C is correct because increasing the instance class of the writer can improve performance. Option A is wrong because read replicas do not help with write latency. Option B is wrong because Auto Scaling does not apply to Aurora instance classes automatically. Option D is wrong because Multi-AZ is already inherent in Aurora.

Answer

Enable Auto Scaling on the cluster to automatically adjust capacity.

Answer

Enable Multi-AZ deployment for the cluster.

Answer

Add more reader instances to distribute the read load.

Question 13

A company is using Amazon DynamoDB with global tables. The application team reports that data written in one region is not immediately available in another region. The database specialist needs to monitor the replication lag. Which CloudWatch metric should be used?

Accepted Answer

Monitor the 'ReplicationLatency' metric in the replica region.. Option B is correct because 'ReplicationLatency' measures the time taken for updates to propagate. Option A is wrong because 'ThrottledRequests' is for throttling. Option C is wrong because 'PendingReplicationCount' shows number of pending items, not time. Option D is wrong because 'ConsumedWriteCapacityUnits' is for capacity.

Answer

Monitor the 'ConsumedWriteCapacityUnits' metric in both regions.

Answer

Monitor the 'PendingReplicationCount' metric in the source region.

Answer

Monitor the 'ThrottledRequests' metric in the source region.

Question 14

A database specialist is troubleshooting a slow Amazon RDS for PostgreSQL query. The specialist has enabled Performance Insights and sees that the database load is high. Which additional tool can provide detailed information about the specific queries causing the load?

Accepted Answer

Use Enhanced Monitoring to view OS-level metrics and correlate with performance insights.. Option B is correct because Enhanced Monitoring provides OS-level metrics, while Performance Insights provides query-level details. Option A is wrong because CloudWatch Logs is for log files. Option C is wrong because AWS CloudTrail is for API calls. Option D is wrong because VPC Flow Logs capture network traffic.

Answer

Use VPC Flow Logs to analyze network traffic to the database.

Answer

Use Amazon CloudWatch Logs to analyze the PostgreSQL error logs.

Answer

Use AWS CloudTrail to view database API calls.

Question 15

A database specialist is monitoring an Amazon RDS for MySQL instance and notices that the 'CPUUtilization' metric is consistently above 90%. Which TWO actions should the specialist take to investigate the issue? (Select TWO.)

Accepted Answer

Use Performance Insights to identify the queries that are consuming the most CPU.. Option A is correct because Performance Insights can identify high-load queries. Option B is correct because Enhanced Monitoring provides OS-level metrics like CPU, memory, and disk I/O. Option C is wrong because increasing instance class is a solution, not an investigation step. Option D is wrong because enabling Multi-AZ does not help investigate CPU usage. Option E is wrong because disabling query cache is not a diagnostic action.

Answer

Disable the MySQL query cache to free up CPU.

Answer

Increase the instance class to provide more CPU resources.

Answer

Enable Multi-AZ to distribute the load to a standby instance.