DBS-C01 Monitoring and Troubleshooting Practice Test 17 — 15 Questions

Question 1

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 2

Refer to the exhibit. A DBA is troubleshooting an issue where an IAM user cannot view CloudWatch metrics for an RDS DB instance. The IAM policy attached to the user is shown above. What is the MOST likely reason the user cannot view the metrics?

Accepted Answer

The policy does not include cloudwatch:DescribeAlarms. The IAM policy includes 'cloudwatch:GetMetricStatistics' and 'cloudwatch:ListMetrics', which should allow retrieving metric data via API. However, the AWS Management Console for CloudWatch Metrics also requires 'cloudwatch:DescribeAlarms' to display alarm overlays on the metrics graph. Without this action, the console may fail to load the metrics page entirely. Option A is correct because the missing permission is 'cloudwatch:DescribeAlarms'. Option B is incorrect because 'rds:DescribeDBInstances' is not needed to view metrics; the policy already includes it. Option C is incorrect because using a Resource of '*' is allowed for CloudWatch actions; it does not prevent viewing metrics. Option D is incorrect because 'cloudwatch:GetMetricStatistics' is already present in the policy.

Answer

The policy does not include rds:DescribeDBInstances

Answer

The policy uses a Resource element of '*' which is not allowed for CloudWatch

Answer

The policy does not include cloudwatch:GetMetricStatistics

Question 3

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

Question 4

Refer to the exhibit. A developer is trying to query the ProductCatalog table using the 'Id' attribute. The query returns no results even though the developer knows data was inserted. What is the MOST likely cause?

Accepted Answer

The table contains no items. The table shows ItemCount: 0, indicating no items exist. Even though data was inserted, if the write operation failed or was directed to a different table, the query returns no results. Option B is incorrect because provisioned throughput issues would cause throttling errors, not zero items. Option C is incorrect because the attribute definition exists (Id is defined). Option D is incorrect because the table status is ACTIVE as shown.

Answer

The provisioned throughput is exceeded

Answer

The attribute definition is missing the 'Id' attribute

Answer

The table is not in ACTIVE status

Question 5

A company is running a production Amazon RDS for MySQL DB instance. The application team reports intermittent connection timeouts. The DBA notices that the DB instance's CPU utilization spikes to 100% during these times. Which metric should be monitored to determine if the issue is due to a specific query?

Accepted Answer

Queries (engine-specific counter). The RDS for MySQL engine-specific counter 'Queries' reflects the number of queries executed. Option A is wrong because DatabaseConnections shows connections, not query performance. Option B is wrong because ReadIOPS measures disk I/O, not query volume. Option C is wrong because NetworkThroughput measures network traffic.

Answer

DatabaseConnections

Answer

NetworkThroughput

Answer

ReadIOPS

Question 6

A company uses Amazon DynamoDB with global tables. During a regional failure, the application in the secondary region experiences higher latency and throttling. The DynamoDB table's WriteCapacityUnits are set to 10000 in both regions. Which action should be taken to reduce throttling during failover?

Accepted Answer

Enable DynamoDB auto scaling for write capacity in both regions. Enabling DynamoDB auto scaling allows the table to dynamically adjust write capacity based on actual traffic, which helps reduce throttling during failover when secondary region traffic increases. Option A is incorrect because switching to on-demand capacity mode may reduce throttling but is more expensive and not the most direct fix for capacity limits; auto scaling provides a more cost-effective solution. Option C is incorrect because disabling global tables would stop cross-region replication, defeating the purpose of multi-region disaster recovery. Option D is incorrect because increasing write capacity of only the secondary region to 20000 may lead to over-provisioning and cost, while auto scaling provides a more efficient and automated solution to handle varying load.

Answer

Switch the table to on-demand capacity mode

Answer

Disable global tables and use application-level replication

Answer

Increase the write capacity of the secondary region to 20000

Question 7

A developer notices that an Amazon RDS for PostgreSQL DB instance is running low on free storage space. The instance has 100 GB of allocated storage. What is the recommended first step to troubleshoot this issue?

Accepted Answer

Check for unused indexes or table bloat using pg_repack or similar tools. Checking for unused indexes or bloat is a typical starting point for storage issues. Option A is wrong because enabling storage auto scaling is a preventive measure, not a troubleshooting step. Option B is wrong because modifying storage is a solution, not a troubleshooting step. Option D is wrong because deleting transaction logs may not recover significant space and can affect point-in-time recovery.

Answer

Enable storage auto scaling

Answer

Modify the DB instance to increase allocated storage

Answer

Delete the oldest transaction logs

Question 8

A company is running an Amazon Aurora MySQL-Compatible DB cluster. The application is experiencing increased latency during peak hours. The DB cluster's CPU utilization is at 40%, but the ReadReplicaLag metric is high. Which of the following is the most likely cause?

Accepted Answer

The writer instance is experiencing I/O bottlenecks, causing slow replication. High replica lag indicates the replica is falling behind, often due to insufficient I/O capacity on the writer or replica. Option B is wrong because read replicas handle SELECT queries. Option C is wrong because the DB cluster parameter group is shared and misconfiguration is not the most likely cause for high replica lag. Option D is wrong because binary log retention period does not affect replica lag directly.

Answer

The read replica is receiving too many write requests

Answer

The DB cluster parameter group is misconfigured

Answer

The binary log retention period is too long

Question 9

A company is using Amazon DynamoDB Accelerator (DAX) to improve read performance. Recently, the cache hit ratio has dropped significantly. The application uses strongly consistent reads. What is the most likely cause of the low cache hit ratio?

Accepted Answer

The application is using strongly consistent reads, which bypass the DAX cache. DAX (DynamoDB Accelerator) is designed to cache data for eventually consistent reads only. When an application uses strongly consistent reads, those requests bypass the DAX cache entirely and go directly to DynamoDB, resulting in a low cache hit ratio. Option A is incorrect because low write capacity may cause throttling but does not directly affect the cache hit ratio. Option C is incorrect because having too few nodes can impact performance and availability, but the primary cause of the drop in cache hits is the consistency model mismatch. Option D is incorrect because while a low TTL can reduce cache effectiveness, the key issue here is that strongly consistent reads never use the cache.

Answer

The DynamoDB table's write capacity is too low

Answer

The DAX cluster has too few nodes

Answer

The DAX cluster's TTL is set too low

Question 10

A database administrator is monitoring an Amazon RDS for SQL Server DB instance and notices that the FreeableMemory metric is consistently below 200 MB. Which of the following actions is most appropriate to mitigate performance issues?

Accepted Answer

Scale up the DB instance to a larger instance class with more memory. A low FreeableMemory metric consistently below 200 MB indicates memory pressure on the RDS for SQL Server DB instance. The most effective mitigation is to scale up to a larger instance class with more memory, directly addressing the resource shortage. Option D is correct because it increases available memory. Option B is incorrect because disabling SQL Server Agent and error logging does not free significant memory and may disrupt essential operations. Option A is incorrect because changing the maintenance window does not affect memory usage. Option C is incorrect because enabling backups with a shorter retention period does not impact memory.

Answer

Modify the DB instance's maintenance window to off-peak hours

Answer

Disable the SQL Server Agent and error logging

Answer

Enable automatic backups with a shorter retention period

Question 11

A company is using Amazon Redshift for data warehousing. The query performance has degraded over time. The DBA suspects that the distribution style of large tables is suboptimal. Which Redshift system view should be queried to identify distribution skew?

Accepted Answer

SVV_DISKUSAGE. SVV_DISKUSAGE provides disk usage per slice, which helps identify distribution skew. Option A is wrong because STL_SCAN provides details about scan operations, not skew. Option B is wrong because PG_TABLE_DEF shows table definitions, not skew. Option D is wrong because STV_TBL_PERM shows storage usage per table but not per slice, making it less suitable for skew analysis.

Answer

STL_SCAN

Answer

PG_TABLE_DEF

Answer

STV_TBL_PERM

Question 12

An application using Amazon DynamoDB is experiencing higher than expected read costs. The table uses on-demand capacity mode. The read pattern is mostly fetching small items (1 KB) using GetItem. Which of the following is the most cost-effective optimization?

Accepted Answer

Switch to eventually consistent reads for GetItem operations. The most cost-effective because eventually consistent reads consume half the read capacity units (0.5 RCU for items up to 4 KB) compared to strongly consistent reads (1 RCU). Since items are small (1 KB) and the table uses on-demand capacity, halving RCU consumption directly reduces read costs. Option A: Switching to provisioned capacity with auto scaling adds complexity and may not reduce costs if traffic is unpredictable; on-demand is already suitable for variable workloads. Option B: Application-level compression would not significantly reduce RCU consumption because items are already under the 4 KB RCU threshold. Option C: Adding DAX introduces additional cost and primarily improves latency, not read cost, as DAX still charges for reads from DynamoDB.

Answer

Change the table to provisioned capacity mode with auto scaling

Answer

Compress the items using application-level compression

Answer

Use DAX to cache the read results

Question 13

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

Accepted Answer

FreeableMemory. Options A and B are correct. FreeableMemory shows the amount of available memory, and SwapUsage indicates the amount of swap space used. A memory leak causes increasing memory consumption, leading to swapping when free memory is exhausted. Monitoring both metrics together helps detect this pattern. Option C (ReadIOPS) is an I/O metric, not directly memory-related. Option D (DatabaseConnections) is a connection metric, unrelated to memory leak detection. Option E (NetworkThroughput) is a network metric, also not relevant.

Answer

ReadIOPS

Answer

DatabaseConnections

Answer

NetworkThroughput

Question 14

Which THREE steps should be taken to troubleshoot high replica lag in an Amazon Aurora MySQL DB cluster? (Choose THREE.)

Accepted Answer

Review network latency between the writer and replica. Options A, C, and E are correct. High replica lag in Amazon Aurora MySQL can be caused by network latency (A), resource contention on the replica (C), or issues with the replication process itself (E). Option B (increasing instance size) is a mitigation, not a troubleshooting step—you diagnose first. Option D (disabling binary logging) would break replication entirely.

Answer

Increase the instance size of the replica

Answer

Disable binary logging on the writer

Question 15

Which TWO CloudWatch Logs features can be used to monitor and troubleshoot Amazon RDS for SQL Server error logs? (Choose TWO.)

Accepted Answer

Setting metric filters to count error occurrences. The correct answers are B and E. CloudWatch Logs allows real-time monitoring of log streams (E) and setting metric filters to count specific error occurrences (B). Option A (AWS X-Ray) is for distributed tracing, not log monitoring. Option C (exporting to S3) is for archival, not real-time monitoring. Option D (CloudTrail) captures API activity, not database error logs.

Answer

Integrating with AWS X-Ray for trace analysis

Answer

Exporting logs to Amazon S3

Answer

Using AWS CloudTrail to capture log events