DBS-C01 Monitoring and Troubleshooting Practice Test 3 — 15 Questions

Question 1

A developer is using AWS Database Migration Service (DMS) to migrate a database from on-premises to Amazon RDS. The migration task is failing with 'Insufficient memory' error. Which resource should be increased to resolve this?

Accepted Answer

Increase the size of the DMS replication instance.. Option A is correct because the DMS replication instance may have insufficient memory. Increasing its size provides more memory. Option B is wrong because source database memory is not controlled by DMS. Option C is wrong because target RDS instance memory may not be the bottleneck. Option D is wrong because S3 is not involved in the DMS process by default.

Answer

Increase the memory on the source database.

Answer

Increase the Amazon S3 bucket size for staging.

Answer

Increase the memory on the target RDS instance.

Question 2

A developer is trying to connect to an RDS for PostgreSQL instance using the endpoint shown in the exhibit. The connection fails with a timeout. Which of the following is the most likely cause?

Accepted Answer

The security group does not allow inbound traffic on port 5432 from the client IP.. Option B is correct because the port 5432 is the default PostgreSQL port, but the security group may not allow inbound traffic on that port. Option A is wrong because the endpoint is correct. Option C is wrong because Multi-AZ does not affect connectivity. Option D is wrong because there is no encryption requirement implied.

Answer

The endpoint address is incorrect.

Answer

The DB instance requires SSL encryption to connect.

Answer

The DB instance is in a Multi-AZ configuration and requires a different endpoint.

Question 3

A company uses Amazon DynamoDB with auto scaling enabled. They notice that a table's write capacity is frequently throttled during a specific hour each day. The access pattern is uniform across partitions. Which action would resolve the throttling without manual intervention?

Accepted Answer

Increase the minimum provisioned capacity in auto scaling.. Option C is correct because auto scaling should increase capacity to meet demand, but if it is not scaling fast enough, adjusting the scaling policy can help. Option A is wrong because disabling auto scaling is not a solution. Option B is wrong because the pattern is uniform, so partitioning is not the issue. Option D is wrong because DAX is for reads, not writes.

Answer

Enable DynamoDB Accelerator (DAX) to cache writes.

Answer

Disable auto scaling and set a fixed higher capacity.

Answer

Create a larger number of partitions by splitting the table.

Question 4

A company is monitoring an Amazon Aurora MySQL DB cluster. They observe that the AuroraReplicaLagMaximum metric is consistently above 10 seconds. Which action would best reduce the replica lag?

Accepted Answer

Increase the instance size of the reader.. Option B is correct because increasing the instance size of the reader can improve its ability to apply changes faster. Option A is wrong because increasing the writer size may not help if the reader is the bottleneck. Option C is wrong because reducing transaction size helps but may not be feasible. Option D is wrong because Multi-AZ is always enabled for Aurora.

Answer

Increase the instance size of the writer.

Answer

Reduce the number of transactions per second.

Answer

Enable Multi-AZ on the cluster.

Question 5

A database administrator notices that an Amazon RDS for MySQL instance is using 100% of its allocated storage. Which action should be taken first to prevent the instance from becoming inaccessible?

Accepted Answer

Modify the DB instance to increase allocated storage.. Option B is correct because increasing storage is immediate and prevents the instance from going into storage-full state. Option A is wrong because deleting logs may free space temporarily but is not a scalable solution. Option C is wrong because archiving to S3 does not free space. Option D is wrong because it does not solve the immediate issue.

Answer

Create a snapshot and archive it to Amazon S3.

Answer

Delete old binary logs to free up space.

Answer

Reboot the DB instance.

Question 6

A developer receives a 'ResourceNotFoundException' when trying to describe a DynamoDB table. The developer runs the command shown in the exhibit and gets the output. What is the most likely cause?

Accepted Answer

The developer is using a different AWS region or the table name has incorrect case.. Option C is correct because the table is in us-west-2, but the developer may be querying from a different region or the table name is case-sensitive. Option A is wrong because the table is ACTIVE. Option B is wrong because the ARN is present. Option D is wrong because the command succeeded.

Answer

The table is not in ACTIVE state.

Answer

The table ARN is incorrect.

Answer

The developer does not have permission to describe the table.

Question 7

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?

Accepted Answer

DatabaseConnections. Option A is correct because DatabaseConnections tracks the number of client connections. Option B is wrong because ActiveTransactions measures transactions. Option C is wrong because NetworkThroughput measures network traffic. Option D is wrong because ReadIOPS measures disk I/O.

Answer

ActiveTransactions

Answer

ReadIOPS

Answer

NetworkThroughput

Question 8

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.. Option B is correct because Amazon RDS provides the Multi-AZ DB cluster deployment option which includes two readable standby instances, allowing read traffic to be offloaded to the standby to reduce load on the primary. Option A is incorrect because increasing the instance size would increase compute costs. Option C is incorrect because enabling Performance Insights does not reduce read latency. Option D is incorrect because increasing the allocated storage does not directly improve read latency for random reads.

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 9

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.. Option C is correct because a high volume of write operations can cause the primary instance to become overloaded, leading to failover. Option A is incorrect because DatabaseConnections alone does not directly cause failover. Option B is incorrect because ReadLatency is a symptom, not a direct cause of failover. Option D is incorrect because FreeableMemory is not a typical cause of failover.

Answer

FreeableMemory.

Answer

DatabaseConnections.

Answer

ReadLatency.

Question 10

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.. Option A is correct because an open transaction can be rolled back using the ROLLBACK command. Option B is incorrect because Point-in-Time Recovery restores the entire DB instance to a previous timestamp, not just the transaction. Option C is incorrect because ROLLBACK will undo the DELETE. Option D is incorrect because COMMIT would make the DELETE permanent.

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 11

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.. Option D is correct because on-demand capacity mode automatically scales but can throttle if traffic is unevenly distributed across partitions, leading to hot partitions. Option A is incorrect because on-demand mode does not have a per-table limit in the same way provisioned capacity does. Option B is incorrect because DynamoDB does not have a global write limit per account that would cause throttling on a single table. Option C is incorrect because the table uses on-demand capacity mode, not provisioned.

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 12

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.. Option B is correct because 'storage-optimization' is a normal state that occurs when modifying the storage configuration, and no action is required. Option A is incorrect because rebooting does not speed up the optimization. Option C is incorrect because there is no need to restore from snapshot. Option D is incorrect because the modification is in progress, and there is no need to cancel it.

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 13

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.. Option D is correct because increasing the replica instance size can improve its ability to apply changes faster. Option A is incorrect because disabling binary logging would break replication. Option B is incorrect because the replica lag is due to the replica not keeping up, not the primary. Option C is incorrect because Multi-AZ is for high availability, not for reducing replica lag.

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 14

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.. Option C is correct because DynamoDB global tables replicate writes asynchronously; if the replica table in eu-west-1 is not properly configured as a global table replica, replication will fail. Option A is incorrect because global tables do not require VPC endpoints. Option B is incorrect because auto scaling does not affect replication. Option D is incorrect because DynamoDB Streams are used for global tables replication, but disabling them would stop replication, not cause lag.

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 15

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.. Option A is correct because 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.