DBS-C01 Monitoring and Troubleshooting Practice Test 7 — 15 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 developer reports that an application's write requests to a DynamoDB table are failing with ProvisionedThroughputExceededException. The table uses provisioned capacity. Which immediate action will resolve the issue?

Accepted Answer

Implement exponential backoff in the application. The correct immediate action is to implement exponential backoff in the application. This retry mechanism gradually increases wait time between retries, reducing the request rate to stay within provisioned throughput limits. Option A is incorrect because switching to on-demand capacity takes time and is not immediate. Option C is incorrect because DAX is a read cache and does not affect write throughput. Option D is incorrect because deleting GSIs does not resolve write throttling to the base table.

Answer

Switch the table to on-demand capacity

Answer

Enable DynamoDB Accelerator (DAX)

Answer

Delete all global secondary indexes

Question 3

A company notices that its Aurora MySQL cluster has a high number of locks and deadlocks. The application uses read replicas for read scaling. What is the MOST likely cause?

Accepted Answer

Long-running transactions on the writer instance. Long-running transactions on the writer instance hold locks for extended periods, increasing the probability of lock contention and deadlocks. Option A is incorrect because Performance Insights is a monitoring tool and does not cause locks or deadlocks. Option B is incorrect because mismatched instance sizes may affect performance but do not directly cause locks or deadlocks. Option D is incorrect because Aurora read replicas are read-only and cannot perform write operations.

Answer

Performance Insights is enabled

Answer

The writer and reader instances are of different sizes

Answer

Read replicas are performing write operations

Question 4

A company is using Amazon ElastiCache for Redis as a caching layer for a web application. Users report that some cached data is missing, causing slower responses. Which ElastiCache feature should be checked first to understand key evictions?

Accepted Answer

Evictions metric in CloudWatch. The Evictions metric in CloudWatch directly shows the number of keys evicted from ElastiCache for Redis due to memory pressure. This is the first metric to check when cached data is missing, as evictions indicate that the cache is full and items are being removed to make space for new ones. Option A (ReplicationLag) measures replication delay between primary and replica nodes, not related to evictions. Option B (CPUUtilization) shows CPU usage but does not indicate evictions. Option D (CacheHits) shows how often requested keys are found in the cache, but does not show evictions. Therefore, option C is correct.

Answer

ReplicationLag metric

Answer

CPUUtilization metric

Answer

CacheHits metric in CloudWatch

Question 5

A database administrator wants to receive an alert when an RDS instance's storage space drops below 10% of total allocated storage. Which AWS service should be used to set up this alert?

Accepted Answer

Amazon CloudWatch Alarms. Amazon CloudWatch Alarms can monitor the FreeStorageSpace metric for RDS instances and trigger an action (e.g., send an SNS notification) when the storage space drops below 10% of total allocated storage. Option A (Amazon SNS) is a notification service that can be used with CloudWatch Alarms but does not itself monitor metrics. Option B (AWS CloudTrail) records API activity, not storage metrics. Option C (AWS Config) tracks configuration changes. Therefore, Option D is the correct service for setting up the alert.

Answer

Amazon SNS

Answer

AWS CloudTrail

Answer

AWS Config

Question 6

A company's DynamoDB table uses provisioned capacity and has a global table for disaster recovery. Write requests to the replica region are failing with ProvisionedThroughputExceededException even though the replica table shows low consumed capacity. What is the MOST likely cause?

Accepted Answer

The replica table's write capacity is insufficient for replication writes. In DynamoDB global tables, writes to the replica region consume write capacity units (WCUs) on the replica table. If the provisioned write capacity on the replica table is insufficient to handle the replication traffic, the replica will throttle incoming write requests with a ProvisionedThroughputExceededException, even if the consumed capacity appears low because throttling occurs before the write is counted. Option C correctly identifies this cause. Option A is incorrect because auto-scaling adjusts capacity over time but does not directly cause throttling. Option B is incorrect because burst capacity provides short-term flexibility; sustained throttling is due to insufficient capacity, not burst exhaustion. Option D is incorrect because DAX is an in-memory cache for reads and does not affect write operations.

Answer

Auto-scaling is disabled on the replica table

Answer

The replica table is exhausting its burst capacity

Answer

DAX is enabled on the replica table

Question 7

Which TWO metrics should be monitored to detect a memory leak in an RDS for Oracle instance? (Choose 2.)

Accepted Answer

SwapUsage. Options A and B are correct because FreeableMemory shows the available memory, and SwapUsage indicates when the OS uses swap due to memory pressure, which are both signs of a memory leak. Option C is wrong because DatabaseConnections does not directly indicate a memory leak. Option D is wrong because CPUUtilization may be high but is not specific to a memory leak. Option E is wrong because ReadIOPS relates to I/O, not memory.

Answer

DatabaseConnections

Answer

CPUUtilization

Answer

ReadIOPS

Question 8

Which THREE actions should be taken to troubleshoot an Amazon RDS for PostgreSQL instance that is unresponsive? (Choose 3.)

Accepted Answer

Verify that the security group allows inbound traffic on the database port. To troubleshoot an unresponsive Amazon RDS for PostgreSQL instance, the standard initial steps are: C) Verify that the security group allows inbound traffic on the database port – connectivity issues are a common cause of unresponsiveness. D) Check the database error logs in CloudWatch Logs – logs may reveal database-specific errors like out-of-memory or corruption. E) Review CloudWatch metrics for CPU, memory, and disk I/O – high utilization can indicate resource exhaustion. Option A (reboot immediately) is wrong because it may destroy diagnostic evidence. Option B (modify instance class) is premature without first assessing the problem.

Answer

Reboot the DB instance immediately

Answer

Modify the DB instance to a larger instance class

Question 9

Which TWO settings should be verified when troubleshooting an RDS for MySQL instance that has a high number of aborted connections? (Choose 2.)

Accepted Answer

connect_timeout parameter. Options A (connect_timeout) and B (max_allowed_packet) are correct because a low connect_timeout can cause connections to abort if not completed within the time limit, and a low max_allowed_packet can cause large queries to fail, resulting in aborted connections. Option C is incorrect because query_cache_type affects caching, not connection handling. Option D is incorrect because binlog_retention_hours is for binary log retention, unrelated to connections. Option E is incorrect because max_connections limits the total number of simultaneous connections but does not directly cause aborted connections; excessive connection attempts might be due to other issues.

Answer

query_cache_type parameter

Answer

binlog_retention_hours parameter

Answer

max_connections parameter

Question 10

A developer reports that an Amazon RDS for MySQL DB instance is experiencing high CPU utilization. You suspect a specific query is causing the issue. Which CloudWatch metric should you examine to confirm this?

Accepted Answer

CPUUtilization. The CPUUtilization metric directly measures the percentage of CPU usage on the DB instance. While it does not isolate a specific query, it confirms that high CPU utilization is occurring. DatabaseConnections, ReadLatency, and FreeableMemory are not direct indicators of CPU usage.

Answer

DatabaseConnections

Answer

ReadLatency

Answer

FreeableMemory

Question 11

A company runs an Amazon RDS for PostgreSQL instance with Multi-AZ deployment. The primary DB instance fails unexpectedly and a failover occurs. Which action should be taken to minimize downtime during future failovers?

Accepted Answer

Configure an Amazon RDS Proxy to reduce failover time.. Amazon RDS Proxy helps minimize downtime during failovers by maintaining database connections, reducing connection disruption and allowing applications to recover faster. The instance already has Multi-AZ enabled, so simply enabling it again is not a valid action. RDS Proxy provides connection pooling and seamless failover handling. Increasing instance size does not reduce failover time. Read replicas require manual promotion and are not used for automatic failover in RDS for PostgreSQL. Multi-AZ is already enabled, so there is no need to enable it again.

Answer

Increase the DB instance size to reduce failover time.

Answer

Create a read replica in the same region and promote it during failover.

Answer

Enable Multi-AZ deployment to automatically failover to the standby.

Question 12

A team is troubleshooting an Amazon DynamoDB table that is throttling write requests. The table has on-demand capacity mode enabled. Which of the following is the most likely cause of the throttling?

Accepted Answer

The write traffic exceeds the table's previous peak traffic by more than double.. Even with on-demand capacity, DynamoDB can throttle write requests if the write traffic exceeds the table's previous peak traffic by more than double. On-demand capacity is designed to handle traffic spikes up to double the previous peak within a 30-minute window. If the spike surpasses that threshold, throttling may occur. Option B correctly identifies this cause. Option A is incorrect because on-demand mode does not use provisioned capacity. Option C is incorrect because adaptive capacity is a feature of provisioned mode, not on-demand. Option D, an AWS Health event, could cause issues but is not the most likely given normal operation.

Answer

The table has exceeded its provisioned write capacity units.

Answer

The table is not using adaptive capacity.

Answer

There is an active AWS Health event affecting the DynamoDB service.

Question 13

An Amazon RDS for Oracle instance is experiencing high swap usage. Which metric should be monitored to determine if the instance is memory-constrained?

Accepted Answer

SwapUsage. SwapUsage indicates that the instance is using swap space, which is a sign of memory pressure. CPUUtilization is for CPU, not memory. FreeableMemory shows available memory, but swap usage directly indicates memory constraint.

Answer

CPUUtilization

Answer

WriteIOPS

Answer

FreeableMemory

Question 14

A company is using Amazon Neptune and notices that some queries are slow. The DBA wants to identify which queries consume the most time. Which feature should be used?

Accepted Answer

Query profiler. Neptune's query profiler provides detailed information about query execution time. The slow query log only logs queries that exceed a threshold. The audit log is for security events. The performance insights is for RDS, not Neptune.

Answer

Database audit log

Answer

Slow query log

Answer

Performance Insights

Question 15

A company is using Amazon ElastiCache for Redis and notices that the cache hit ratio is low. The application is frequently reading data that is not in the cache. Which action would be most effective in improving the cache hit ratio?

Accepted Answer

Pre-warm the cache by loading frequently accessed data from the database.. Pre-warming the cache (option C) by loading frequently accessed data from the database into the ElastiCache cluster before it is requested increases the likelihood that subsequent reads will hit the cache. This directly improves the cache hit ratio. Increasing replicas (option A) does not add more cache capacity, it only provides read replicas for high availability. Decreasing TTL (option B) causes items to expire sooner, potentially reducing the hit ratio. Enabling Multi-AZ (option D) provides failover but does not affect hit ratio. Therefore, option C is the most effective action.

Answer

Increase the number of replicas in the replication group.

Answer

Decrease the TTL of cached items to ensure freshness.

Answer

Enable Multi-AZ for automatic failover.