DBS-C01 Monitoring and Troubleshooting Practice Test 4 — 15 Questions

Question 1

A company uses Amazon CloudWatch to monitor an RDS for Oracle instance. They want to receive an alert when the database connection count exceeds 90% of the maximum connections. Which CloudWatch metric should be used to create the alarm?

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

Accepted Answer

DatabaseConnections. (DatabaseConnections) is correct because this metric tracks the number of client connections to the database instance, which directly reflects the connection count. To alert when connections exceed 90% of maximum connections, you would monitor DatabaseConnections and compare it to the instance's MaxConnections parameter. Option A (ActiveTransactions) is incorrect because it measures the number of concurrent transactions, not connections. Option C (ReadIOPS) and Option D (NetworkThroughput) are unrelated metrics for disk I/O and network traffic, respectively.

Answer

ActiveTransactions

Answer

ReadIOPS

Answer

NetworkThroughput

Question 2

A company is experiencing high read latency on their Amazon RDS for MySQL Multi-AZ DB instance. The application performs many small, random reads. Which configuration change would most likely reduce the read latency without incurring additional compute costs?

Accepted Answer

Enable Multi-AZ DB cluster deployment with two readable standby instances and route read traffic to the standby.. The Multi-AZ DB cluster deployment for Amazon RDS includes two readable standby instances. By routing read traffic to these standbys, the load on the primary is reduced, which can decrease read latency without additional compute costs since the standbys are already provisioned. Option A is incorrect because increasing allocated storage primarily improves I/O throughput for sequential operations but may not significantly reduce latency for many small random reads. Option B is incorrect because Performance Insights is a monitoring tool that helps identify performance bottlenecks but does not directly reduce read latency. Option D is incorrect because increasing the instance size (e.g., from db.r5.large to db.r5.xlarge) would incur additional compute costs.

Answer

Increase the allocated storage size to improve I/O throughput.

Answer

Enable Performance Insights to monitor and optimize queries.

Answer

Increase the instance size from db.r5.large to db.r5.xlarge.

Question 3

A database team notices that the Amazon Aurora MySQL-Compatible DB cluster is experiencing frequent failovers during peak hours. The failover events are not correlated with any maintenance windows or manual interventions. Which metric in Amazon CloudWatch should be investigated first to identify the root cause?

Accepted Answer

WriteIOPS.. (WriteIOPS) is correct because during peak hours, high write IOPS can overwhelm the primary instance's capacity, leading to replication lag or resource exhaustion that triggers a failover. Monitoring WriteIOPS helps identify if the write workload exceeds the instance's limits. Option A (FreeableMemory) is incorrect because low freeable memory can cause performance degradation but is less likely to directly cause failover unless memory is severely exhausted. Option B (DatabaseConnections) is incorrect because high connection counts can cause performance issues but typically do not directly trigger failovers unless combined with other resource constraints. Option C (ReadLatency) is incorrect because it is a symptom of issues like high read load or replication lag, but not a direct cause of failover; failovers are usually triggered by primary instance failure or unreachability.

Answer

FreeableMemory.

Answer

DatabaseConnections.

Answer

ReadLatency.

Question 4

A developer executed a DELETE statement without a WHERE clause on an Amazon RDS for PostgreSQL instance. The transaction is still open. Which action should the developer take to undo the DELETE without affecting other operations?

Accepted Answer

Execute ROLLBACK in the same session.. The correct action is to execute ROLLBACK in the same session. Since the transaction is still open, issuing ROLLBACK will undo the DELETE statement without affecting other operations. Option A is incorrect because COMMIT would make the DELETE permanent. Option B is incorrect because Point-in-Time Recovery restores the entire DB instance to a past state, which is unnecessary and affects other data. Option D is incorrect because stopping and restoring from a snapshot would also affect other data and is not the simplest solution.

Answer

Execute COMMIT and then run a recovery script.

Answer

Use the Point-in-Time Recovery feature to restore the database to a time before the DELETE.

Answer

Stop the DB instance and restore from the latest snapshot.

Question 5

A company is using Amazon DynamoDB as the primary database for a global e-commerce application. During the holiday season, the application experiences throttling on write requests even though the read and write capacity units are well below the provisioned limits. The table uses on-demand capacity mode. What is the most likely cause of this throttling?

Accepted Answer

There is a hot partition due to an uneven write distribution across partition keys.. In DynamoDB on-demand capacity mode, throughput scales automatically based on traffic. However, throttling can still occur if a single partition receives more write requests than the partition's maximum throughput capacity (1,000 WCU per partition). This is known as a hot partition, caused by an uneven distribution of write activity across partition keys. Option A correctly identifies this. Option B is incorrect because on-demand mode does not use provisioned capacity. Option C uses incorrect terminology—there is no 'maximum write capacity units per partition' that the table as a whole can exceed. Option D is incorrect because DynamoDB does not have a per-region account-level write limit that causes throttling on a single table.

Answer

The table's provisioned write capacity is set too low.

Answer

The table has exceeded the maximum write capacity units per partition.

Answer

The AWS account has reached the DynamoDB write throughput limit per region.

Question 6

A database administrator notices that an Amazon RDS for SQL Server DB instance has been in the 'storage-optimization' state for several hours after modifying the storage type from gp2 to io1. What should the administrator do to resolve this?

Accepted Answer

Wait for the storage optimization to complete.. The 'storage-optimization' state is a normal part of the modification process when converting between storage types on RDS. It can take hours as the database migrates to the new storage configuration. The administrator should simply wait for the process to complete. Options B, C, and D are incorrect: restoring from a snapshot would lose recent changes and requires reapplication of the modification, modifying back to gp2 would interrupt the process and still require time, and rebooting does not affect the storage optimization.

Answer

Restore from the latest snapshot and reapply the modification.

Answer

Cancel the modification by modifying the DB instance back to gp2.

Answer

Reboot the DB instance.

Question 7

A development team is using Amazon RDS for MySQL with read replicas to offload reporting queries. They notice that the read replica is consistently lagging behind the primary by several seconds. The primary handles 5000 writes per second. Which action would most likely reduce replica lag?

Accepted Answer

Increase the instance size of the read replica.. Increasing the instance size of the read replica provides more CPU and memory resources, allowing it to apply changes from the binary log faster, thereby reducing replica lag. Option A is incorrect because increasing 'max_connections' on the primary does not affect the replica's ability to apply changes; it only allows more connections to the primary. Option C is incorrect because disabling binary logging on the primary would break replication entirely, as the replica relies on the binary log to receive changes. Option D is incorrect because converting the primary to Multi-AZ improves availability and failover but does not directly reduce replication lag on the read replica.

Answer

Increase the 'max_connections' parameter on the primary instance.

Answer

Disable binary logging on the primary instance to reduce I/O.

Answer

Convert the primary instance to a Multi-AZ deployment.

Question 8

A company is using Amazon DynamoDB with global tables to support a multi-region application. They notice that writes to the table in us-east-1 are not replicating to the table in eu-west-1. The replication lag metric shows increasing values. What is the most likely cause?

Accepted Answer

The table in eu-west-1 has been removed as a replica region from the global table configuration.. If the replica region (eu-west-1) has been removed from the global table configuration, DynamoDB will stop replicating writes to that region, and the replication lag metric will show increasing values. Option A is incorrect: while a lower write capacity in eu-west-1 could cause throttling and replication lag, it would not completely stop replication; the lag metric would still show some activity. Option B is incorrect: DynamoDB Streams must be enabled on the source table for global tables to function, but disabling them would halt replication entirely, not cause increasing lag. Option C is incorrect: global tables replicate asynchronously over DynamoDB's internal network and do not require VPC connectivity between regions.

Answer

The table in eu-west-1 has a lower write capacity and is throttling incoming writes.

Answer

DynamoDB Streams is disabled on the table in us-east-1.

Answer

The DynamoDB table in us-east-1 is not accessible from eu-west-1 due to VPC restrictions.

Question 9

A team is using Amazon RDS for Oracle with an option group that includes the Oracle Enterprise Manager (OEM) option. After modifying the option group to add a new option, the DB instance is stuck in the 'modifying' state for an extended period. What should the team do?

Accepted Answer

Reboot the DB instance to complete the modification.. Adding certain options may require a reboot. Option B is incorrect because the option group modification is likely valid; the issue is that it requires a reboot. Option C is incorrect because modifying the DB instance again would not help. Option D is incorrect because the DB instance is not in a failed state.

Answer

Contact AWS Support to force the modification.

Answer

Create a new DB instance with the desired options and migrate the data.

Answer

Modify the DB instance again to reset the state.

Question 10

An administrator is troubleshooting an Amazon RDS for PostgreSQL instance that is experiencing high CPU utilization. The administrator has enabled Performance Insights. Which metric should be examined first to identify the queries consuming the most CPU?

Accepted Answer

db.load.avg. The correct metric to examine first is 'db.load.avg' (Option C). In Amazon RDS Performance Insights, 'db.load.avg' represents the average number of active sessions, which directly correlates with CPU utilization. A high value indicates queries that are consuming significant CPU resources. Option A ('db.sessions') is not a standard Performance Insights metric. Option B ('db.cpu.avg') does not exist in Performance Insights. Option D ('db.bytes_sent') is a network metric unrelated to CPU usage.

Answer

db.sessions

Answer

db.cpu.avg

Answer

db.bytes_sent

Question 11

Which TWO actions can help reduce Amazon RDS for MySQL replication lag between a primary instance and a read replica? (Choose two.)

Accepted Answer

Reduce the number of write-heavy DML statements on the primary.. Reducing write-heavy DML on the primary (Option B) decreases the volume of changes to be replicated, directly reducing lag. Increasing the instance size of the read replica (Option D) provides more CPU and memory resources for applying changes from the binary log. Option A is incorrect because increasing allocated storage does not improve the replica's ability to apply changes; it only increases storage capacity. Option C is incorrect because enabling Multi-AZ on the primary provides high availability but does not reduce replication lag. Option E is incorrect because binary logging is required for replication; disabling it would break replication.

Answer

Increase the allocated storage for the read replica.

Answer

Enable Multi-AZ on the primary instance.

Answer

Disable binary logging on the primary instance.

Question 12

Which THREE metrics should be monitored in Amazon CloudWatch to detect a potential memory leak in an Amazon RDS for SQL Server instance? (Choose three.)

Accepted Answer

DatabaseConnections. Options A, D, and E are correct. DatabaseConnections can indicate a memory leak if connections are not closed, consuming memory. SwapUsage indicates memory pressure when physical memory is insufficient. FreeableMemory shows available memory; a decreasing trend may suggest a leak. Option B is incorrect because CPUUtilization is not a direct memory metric. Option C is incorrect because ReadIOPS relates to I/O operations, not memory.

Answer

CPUUtilization

Answer

ReadIOPS

Question 13

Which TWO AWS services can be used to monitor the performance of an Amazon DynamoDB table and send alerts when throttling occurs? (Choose two.)

Accepted Answer

Amazon CloudWatch Alarms. Amazon CloudWatch provides metrics such as ConsumedReadCapacityUnits, ConsumedWriteCapacityUnits, and ThrottledRequests for DynamoDB. You can create CloudWatch Alarms to monitor these metrics and send notifications (e.g., via SNS) when throttling occurs. Therefore, both B (CloudWatch Alarms) and E (CloudWatch) are correct. Option A (Amazon Inspector) is a security assessment service, not a monitoring service. Option C (VPC Flow Logs) captures network traffic, not database performance. Option D (AWS Config) tracks resource configuration changes, not performance metrics.

Answer

Amazon Inspector

Answer

VPC Flow Logs

Answer

AWS Config

Question 14

Refer to the exhibit. A database administrator runs the AWS CLI command to describe events for an RDS instance. Which conclusion is most likely correct based on the output?

Accepted Answer

The DB instance experienced a Multi-AZ failover and subsequently restarted.. The output shows a failover event followed by a restart, which is typical after a failover. Option A is incorrect because the events show a failover, not a manual restart. Option B is incorrect because the failover was completed, not failed. Option D is incorrect because there is no indication of a snapshot restore.

Answer

The Multi-AZ failover failed and the instance restarted.

Answer

The DB instance was manually restarted by an administrator.

Answer

The DB instance was restored from a snapshot and then restarted.

Question 15

Refer to the exhibit. An IAM policy is attached to a user who is attempting to run a Scan operation on the Orders table using the AWS CLI. The Scan operation fails with an AccessDeniedException. What is the most likely reason?

Accepted Answer

The 'ForAllValues:StringEquals' condition set operator prevents the Scan operation because it requires all leading keys to match a single value, which is impossible for a Scan.. The condition 'dynamodb:LeadingKeys' applies only to Query and Scan operations when the condition key is used to restrict partition key values. However, the condition 'ForAllValues:StringEquals' requires that all leading keys in the request match the specified value. For a Scan operation without a specific partition key, the condition cannot be satisfied, leading to denial. Option A is incorrect because the resource ARN includes the table name, so it is valid. Option B is incorrect because the policy allows Scan action. Option C is incorrect because the condition is on LeadingKeys, not on the table.

Answer

The resource ARN does not include the table name.

Answer

The Scan action is not allowed in the policy.

Answer

The condition requires the partition key to be 'CustomerID', but the Scan operation does not specify a partition key.