DBS-C01 Monitoring and Troubleshooting Practice Test 18 — 15 Questions

Question 1

A database specialist is troubleshooting an Amazon RDS for MySQL DB instance that is running out of storage. The instance has automated backups enabled. The specialist needs to free up storage space immediately without losing backup capability. Which action should the specialist take?

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

Accepted Answer

Delete older automated backups that are no longer needed.. None of the provided options will free up DB instance storage. Automated backups are stored in Amazon S3, not in the instance's allocated storage. To free up instance storage, you would need to increase the allocated storage or delete actual data from the database. Reducing backup retention deletes backups from S3, not instance storage. Manual snapshots are also in S3. Disabling backups stops future backups but does not free existing storage.

Answer

Modify the DB instance to reduce the backup retention period to 0 days.

Answer

Delete manual snapshots from the RDS console.

Answer

Disable automated backups to stop storage consumption.

Question 2

Refer to the exhibit. A database specialist is investigating performance degradation on an Amazon RDS for MySQL DB instance. The BurstBalance metric shows the values above. What does this indicate, and what action should be taken?

Accepted Answer

The instance has exhausted its I/O burst credits; scale up the allocated storage to increase baseline I/O.. The BurstBalance metric on Amazon RDS reflects the remaining I/O credits for gp2 (and earlier magnetic) storage. When BurstBalance drops to zero, the instance can no longer burst above its baseline IOPS, causing performance degradation. The correct action is to scale up the allocated storage size, which increases the baseline IOPS for gp2, or migrate to gp3/provisioned IOPS storage to decouple performance from capacity.

Answer

The instance is experiencing high read load; add a read replica to offload reads.

Answer

The instance's compute capacity is insufficient; change the instance class to a larger size.

Answer

The instance is experiencing a memory bottleneck; enable Performance Insights to analyze query performance.

Question 3

A company is running an Amazon RDS for MySQL database. The application team reports that the database is slow. Upon investigation, you notice that the DB instance's CPU utilization is consistently above 90%. Which initial troubleshooting step should you take?

Accepted Answer

Enable Enhanced Monitoring to identify the source of high CPU usage.. When CPU utilization is consistently above 90% on an RDS for MySQL instance, the correct first step is to gather diagnostic data rather than blindly scaling. Enhanced Monitoring provides OS-level metrics (per-process CPU, memory, disk I/O) at up to 1-second granularity, which lets you pinpoint whether the CPU is consumed by the MySQL process, a specific query, or an external agent. Only after identifying the root cause can you choose the right remediation, such as query tuning, indexing, or a vertical scale.

Answer

Increase the DB instance size to improve performance.

Answer

Delete the slow query logs to reduce I/O.

Answer

Change the storage type from General Purpose (gp2) to Provisioned IOPS (io1).

Question 4

A developer is troubleshooting an application that uses Amazon DynamoDB. The application is experiencing throttled requests (ProvisionedThroughputExceededException). Which CloudWatch metric should be monitored to troubleshoot this issue?

Accepted Answer

ThrottledRequests. ThrottledRequests is a CloudWatch metric that directly counts the number of requests that were throttled due to exceeding provisioned throughput. For troubleshooting throttling issues, this metric provides immediate visibility into when throttling occurs. ConsumedWriteCapacityUnits (option D) shows capacity usage but does not directly indicate throttling; high consumption may lead to throttling but is not a direct measure. SuccessfulRequestLatency (option B) measures latency, not throttling, and UserErrors (option C) tracks client-side errors like invalid parameters, not capacity-related throttling.

Answer

SuccessfulRequestLatency

Answer

UserErrors

Answer

ConsumedWriteCapacityUnits

Question 5

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 6

A company is running an Amazon RDS for Oracle database in Multi-AZ. The primary instance fails over unexpectedly. The DBA wants to determine the cause of the failover. What should the DBA do?

Accepted Answer

View the RDS events in the AWS Management Console.. RDS events in the AWS Management Console (or via the describe-events API) capture Multi-AZ failover events, including the reason and timestamp, such as 'Multi-AZ failover started' or 'DB instance restarted.' This is the authoritative source for determining why a failover occurred, because RDS logs the failover trigger (e.g., primary instance failure, storage issue, or manual reboot) as an event. Reviewing these events gives the DBA the exact cause without needing to dig into OS-level metrics or database logs.

Answer

Review the Enhanced Monitoring metrics for the primary instance.

Answer

Query the database error logs for the failover time.

Answer

Check AWS CloudTrail for any database-related API calls.

Question 7

A company is using Amazon ElastiCache for Redis as a caching layer. The application performance degrades when cache misses increase. Which metric should be monitored to track the cache hit rate?

Accepted Answer

CacheHits and CacheMisses. The cache hit rate is calculated directly from the CacheHits and CacheMisses CloudWatch metrics — hit rate = CacheHits / (CacheHits + CacheMisses). Monitoring both is the only way to quantify how often the application is served from Redis versus forced to fall back to the origin database. This is the standard ElastiCache metric pair for diagnosing cache effectiveness.

Answer

CurrConnections

Answer

CPUUtilization

Answer

Evictions

Question 8

A database administrator notices that an Amazon RDS for MySQL DB instance is using more storage than expected. Which metric should be monitored to troubleshoot storage usage?

Accepted Answer

FreeStorageSpace. FreeStorageSpace is the CloudWatch metric that reports the amount of available storage in bytes on an RDS instance. Monitoring this metric is the direct way to troubleshoot unexpected storage consumption, as it shows how much space remains and helps correlate with data growth, binary logs, or temporary files. A declining FreeStorageSpace trend indicates the need to investigate table growth, log retention, or storage autoscaling settings.

Answer

DatabaseConnections

Answer

ReadIOPS

Answer

NetworkThroughput

Question 9

A company is running an Amazon DocumentDB cluster. The application is experiencing high write latency. The cluster has a single instance. What should be done to identify the cause of the latency?

Accepted Answer

Enable Performance Insights and review the top wait events.. Enabling Performance Insights for Amazon DocumentDB allows you to monitor the database load and review top wait events, which helps identify the specific causes of high write latency, such as lock contention or I/O bottlenecks. Option A is wrong because simply upgrading to a larger instance size addresses symptoms but does not identify the root cause. Option C is wrong because adding a replica does not reduce write latency on the primary instance; it only offloads read traffic. Option D is wrong because changing to Provisioned IOPS may improve I/O performance but does not diagnose the underlying issue causing latency.

Answer

Upgrade the instance to a larger size.

Answer

Add a replica to distribute the write load.

Answer

Change the storage type to Provisioned IOPS.

Question 10

A database specialist notices that an RDS MySQL instance's FreeableMemory metric is consistently below 100 MB. Which monitoring tool should be used to identify the queries consuming the most memory?

Accepted Answer

Performance Insights. Performance Insights is the correct tool because it provides detailed monitoring of database load and allows you to identify the queries consuming the most memory. It visualizes database load by wait events and top SQL, helping pinpoint memory-intensive queries. FreeableMemory is an OS-level metric, but Performance Insights drills down to the SQL level.

Answer

Amazon S3 access logs

Answer

AWS CloudTrail

Answer

CloudWatch Logs

Question 11

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 12

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 tracks the number of keys evicted from the cache due to memory pressure. When ElastiCache for Redis reaches its maxmemory limit, it evicts keys according to the configured eviction policy (e.g., volatile-lru, allkeys-lru). Monitoring this metric first will confirm whether missing cached data is caused by evictions. Other metrics like CacheHits or CPUUtilization do not provide direct insight into eviction events.

Answer

ReplicationLag metric

Answer

CPUUtilization metric

Answer

CacheHits metric in CloudWatch

Question 13

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 is the correct service because it evaluates CloudWatch metrics against thresholds and triggers actions such as SNS notifications. For RDS, the FreeStorageSpace metric can be compared to a percentage of allocated storage using a metric math expression, and an alarm can fire when it drops below 10%. CloudWatch is the native monitoring and alerting layer for RDS.

Answer

Amazon SNS

Answer

AWS CloudTrail

Answer

AWS Config

Question 14

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

Accepted Answer

SwapUsage. SwapUsage (A) is correct because a memory leak in RDS for Oracle causes the instance to exhaust physical RAM and begin paging to the swap file, so rising SwapUsage is a direct indicator of memory pressure from a leak. FreeableMemory (B) is correct because it reports the amount of available RAM on the DB instance; a steadily declining FreeableMemory trend over time, without a corresponding workload increase, is the classic signature of a memory leak. DatabaseConnections (C) is not correct because it only counts active sessions and does not measure memory consumption. CPUUtilization (D) is not correct because high CPU can stem from many causes and does not specifically indicate leaked memory. ReadIOPS (E) is not correct because it measures read I/O operations, which may rise with swapping but is not a direct memory-leak metric.

Answer

DatabaseConnections

Answer

CPUUtilization

Answer

ReadIOPS

Question 15

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. Option C is correct because an unresponsive RDS for PostgreSQL instance is often caused by network-level blocking; verifying that the associated security group permits inbound traffic on the PostgreSQL port (5432) confirms clients can actually reach the endpoint. Option D is correct because RDS publishes PostgreSQL logs to CloudWatch Logs when the relevant log exports are enabled, and reviewing postgresql.log and upgrade logs reveals errors such as crashes, out-of-memory events, or replication failures that explain the unresponsiveness. Option E is correct because CloudWatch metrics like CPUUtilization, FreeableMemory, and DiskQueueDepth/ReadIOPS/WriteIOPS show whether resource exhaustion (CPU saturation, memory pressure, or storage I/O bottlenecks) is the root cause. Option A is not appropriate as a first troubleshooting step because rebooting is a disruptive remediation action that destroys diagnostic state and should follow, not precede, investigation. Option B is also not a troubleshooting action; resizing the instance class is a scaling change that may mask the symptom without identifying the underlying cause and can cause downtime.

Answer

Reboot the DB instance immediately

Answer

Modify the DB instance to a larger instance class