DBS-C01 Monitoring and Troubleshooting Practice Test 22 — 15 Questions

Question 1

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?

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

Accepted Answer

FreeableMemory. FreeableMemory (B) is correct because it reports the amount of available RAM in bytes on the RDS instance, so a declining value directly indicates that PostgreSQL is consuming more memory than expected. SwapUsage (E) is correct because it shows how much memory has been pushed to the swap file; rising swap usage signals memory pressure and confirms that the instance is exhausting physical RAM. Together these two CloudWatch metrics let the DBA distinguish normal cache growth from genuine memory exhaustion. NetworkReceiveThroughput (A) measures inbound network traffic, ReadIOPS (C) measures disk read operations per second, and DatabaseConnections (D) counts active client sessions — none of these directly report memory consumption, so they cannot diagnose the memory issue on their own.

Answer

NetworkReceiveThroughput

Answer

ReadIOPS

Answer

DatabaseConnections

Question 2

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.. Performance Insights provides detailed database performance metrics and helps identify bottlenecks such as high load or slow queries. Option B is wrong because AWS Config tracks configuration changes, not performance. Option C is wrong because CloudWatch Metrics Dashboard shows aggregated metrics but lacks the granular database analysis needed for root cause identification. Option D is wrong because Amazon Inspector is a security assessment tool, not a performance monitoring service.

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 3

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.. The correct CloudWatch metric for free storage space on an RDS instance is 'FreeStorageSpace', which is reported in bytes. To set an alarm for when free space drops below 50 GB, you must convert 50 GB to bytes: 50 * 1024^3 = 53,687,091,200 bytes. Therefore, the threshold should be 53687091200.

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 4

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.. The cache hit ratio is calculated as CacheHits / (CacheHits + CacheMisses). Monitoring the 'CacheHits' and 'CacheMisses' CloudWatch metrics allows the specialist to compute the hit ratio and confirm whether it has decreased, which would explain increased latency. Option A is incorrect because CurrConnections shows the number of connections, not the cache hit ratio. Option B is incorrect because Evictions indicates keys being evicted, which can affect the cache but does not directly measure the hit ratio. Option D is incorrect because ReplicationLag measures replication delay, not cache performance.

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 5

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.. The 'Connection timed out' error suggests the packet is being dropped at the network layer, likely by a network ACL. Since the security group allows inbound on port 3306, the next step is to check the network ACL associated with the RDS instance's subnet. Network ACLs are stateless, so they must allow both inbound traffic on port 3306 and outbound traffic on ephemeral ports for the response. Option B is incorrect because a timed out error occurs before the TCP handshake completes, so DNS resolution is not the issue. Option C is incorrect because an internet gateway and public route are irrelevant if both instances are in the same VPC or connected privately. Option D is incorrect because the security group for the EC2 instance can be stateful and typically allows outbound traffic by default; the timeout is not caused by missing outbound rules on the EC2 side.

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 6

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.. High write latency on an Aurora MySQL cluster is typically caused by the writer instance's resource constraints (CPU, memory, or I/O). Increasing the instance class of the writer instance provides more compute and memory resources, which directly improves write throughput and reduces latency. Reader instances and Auto Scaling do not address writer-side write latency because writes only go to the writer.

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 7

A company is using Amazon DynamoDB with provisioned capacity. The application is experiencing throttling on write requests. The database specialist needs to identify the cause. Which TWO metrics should be reviewed in CloudWatch? (Select TWO.)

Accepted Answer

ConsumedWriteCapacityUnits. 'ConsumedWriteCapacityUnits' shows the actual write capacity used, helping to determine if provisioned capacity is exceeded, which leads to throttling. Option B is correct because 'WriteThrottleEvents' directly indicates the number of throttled write requests. Option C is incorrect because 'ThrottledWriteRequests' is not a valid CloudWatch metric for DynamoDB; the correct metric for throttled writes is 'WriteThrottleEvents'. Option D is incorrect because 'ReadThrottleEvents' pertains to read throttling, not writes. Option E is incorrect because 'SuccessfulRequestLatency' measures latency, not throttling events.

Answer

ThrottledWriteRequests

Answer

ReadThrottleEvents

Answer

SuccessfulRequestLatency

Question 8

A company uses Amazon RDS for MySQL with Multi-AZ deployment. The database is experiencing increased latency and the application team reports slow queries. The DBA wants to identify the queries that consume the most resources. Which AWS service should be used to capture and analyze these queries?

Accepted Answer

Amazon RDS Performance Insights. Amazon RDS Performance Insights provides database performance tuning and monitoring with query-level metrics, enabling identification of resource-intensive queries. Option B is wrong because CloudWatch Logs collects log files but does not capture query-level performance. Option C is wrong because Enhanced Monitoring provides OS-level metrics (CPU, memory) but not query-level details. Option D is wrong because CloudTrail records AWS API activity, not database queries.

Answer

Amazon CloudWatch Logs

Answer

Amazon RDS Enhanced Monitoring

Answer

AWS CloudTrail

Question 9

A company is using Amazon Redshift for data warehousing. The VACUUM operation is taking longer than expected, and the database administrator wants to identify the tables that require the most vacuuming effort. Which system table should be queried to find the percentage of deleted rows per table?

Accepted Answer

SVV_TABLE_INFO. (SVV_TABLE_INFO) is correct because this system table contains tombstone and unsorted statistics, including the percentage of deleted rows per table, which helps identify tables requiring vacuuming. Option A (STL_QUERY) is incorrect because it stores query execution logs, not table statistics. Option B (STV_TBL_PERM) is incorrect as it provides information about permanent table block allocations but not deleted row ratios. Option C (PG_TABLE_DEF) is incorrect because it holds table schema definitions only, not operational metrics.

Answer

STL_QUERY

Answer

STV_TBL_PERM

Answer

PG_TABLE_DEF

Question 10

A developer is troubleshooting an issue where an application using Amazon DynamoDB is receiving occasional 'ThrottlingException' errors. The application uses eventually consistent reads. What is the MOST likely cause of this error?

Accepted Answer

The read capacity units are set too low for the current traffic pattern. ThrottlingException in DynamoDB is returned when the request rate exceeds the provisioned read or write capacity of a table or its indexes. Since the application uses eventually consistent reads (which consume only half the RCU of strongly consistent reads), the most likely cause is that the provisioned RCU is simply insufficient for the current traffic pattern. The fix is to increase RCU, enable auto scaling, or switch to on-demand capacity mode.

Answer

The application is using an incorrect table name

Answer

The application is using eventually consistent reads instead of strongly consistent reads

Answer

There is a network connectivity issue between the application and DynamoDB

Question 11

A company is using Amazon ElastiCache for Redis as a caching layer for a web application. The application's response time has increased, and the operations team suspects that cache evictions are occurring frequently. Which ElastiCache metric should be monitored to confirm cache evictions?

Accepted Answer

Evictions. The Evictions metric in Amazon ElastiCache for Redis shows the number of keys evicted due to memory pressure. Option A (CacheHits) is wrong because it indicates successful key retrievals, not evictions. Option B (SwapUsage) is wrong because it shows the amount of swap space used, not eviction count. Option D (CurrItems) is wrong because it shows the current number of items in the cache, not evictions.

Answer

CacheHits

Answer

SwapUsage

Answer

CurrItems

Question 12

A database administrator is troubleshooting an issue where an Amazon RDS for PostgreSQL DB instance is not allowing connections. The administrator checks the security group and network ACLs, and they are correctly configured. What is the next step to diagnose the issue?

Accepted Answer

Review the DB instance error logs in Amazon CloudWatch. When security groups and network ACLs are correctly configured but an RDS for PostgreSQL instance still refuses connections, the next diagnostic step is to review the DB instance error logs in Amazon CloudWatch. These logs often reveal the root cause, such as the instance being in a failed state, a parameter misconfiguration, or an internal error preventing the database from accepting connections.

Answer

Reboot the DB instance

Answer

Modify the DB instance's parameter group

Answer

Create a DB snapshot

Question 13

A company is using Amazon DynamoDB and wants to monitor the read/write capacity utilization of a table. Which ONE AWS service can be used to set up alarms for capacity consumption?

Accepted Answer

Amazon CloudWatch. Amazon CloudWatch is the AWS service designed to monitor metrics and set alarms. DynamoDB automatically publishes metrics such as ConsumedReadCapacityUnits and ConsumedWriteCapacityUnits to CloudWatch. You can create CloudWatch alarms on these metrics to trigger actions when capacity utilization exceeds thresholds, enabling proactive management of table performance.

Answer

Amazon DynamoDB Auto Scaling

Answer

AWS CloudTrail

Answer

Amazon CloudWatch Logs

Answer

AWS Config

Question 14

A company is using Amazon Redshift and has a query that is running slowly. The DBA wants to identify if the query is I/O-bound. Which TWO metrics from Amazon CloudWatch can indicate I/O-bound queries?

Accepted Answer

ReadIOPS. Options B and E are correct. ReadIOPS measures the number of read I/O operations per second, and ReadLatency measures the average time per read I/O operation. High values for these metrics indicate that the query is I/O-bound. Option A (NetworkReceiveThroughput) measures network throughput, not I/O. Option C (CPUUtilization) indicates CPU-bound workloads. Option D (WriteIOPS) measures write I/O, which is less likely to be the primary indicator for a slow query, and the question asks for the two metrics that can indicate I/O-bound queries; ReadIOPS and ReadLatency are the most direct I/O metrics.

Answer

NetworkReceiveThroughput

Answer

CPUUtilization

Answer

WriteIOPS

Question 15

Refer to the exhibit. A DBA sees the above error log entries for an Amazon RDS for MySQL DB instance. Which action should the DBA take to resolve the 'Too many connections' error?

Accepted Answer

Modify the DB parameter group to increase max_connections. Increasing the max_connections parameter in the DB parameter group allows the MySQL instance to handle more concurrent connections, directly resolving the 'Too many connections' error. Option B is incorrect because rebooting the DB instance does not change the connection limit, only temporarily clears existing connections. Option C is incorrect because modifying the DB security group adjusts network access rules, not the database's internal connection limit. Option D is incorrect because resetting the master user password addresses authentication issues, not the connection limit.

Answer

Reboot the DB instance

Answer

Modify the DB security group to allow more connections

Answer

Reset the DB instance master user password