DBS-C01 Management and Operations Practice Test 5 — 15 Questions

Question 1

A database specialist is managing an Amazon RDS for Oracle DB instance. The instance has a large amount of data and the specialist needs to migrate it to a new instance in a different AWS Region. Which method would minimize downtime and be the most efficient?

Accepted Answer

Use AWS Database Migration Service (DMS) with ongoing replication to migrate to the target instance.. Option C is correct. AWS Database Migration Service (DMS) with ongoing replication minimizes downtime and supports cross-region migration. Option A is wrong because exporting to S3 and importing is time-consuming and does not support ongoing replication. Option B is wrong because cross-region read replicas are not available for Oracle. Option D is wrong because RMAN backups are not integrated with AWS for cross-region migration.

Answer

Export the database to Amazon S3 using Oracle Data Pump, then import into the new instance.

Answer

Create a cross-region read replica and promote it.

Answer

Take a full backup using Oracle RMAN, copy the backup files to the target region, and restore.

Question 2

A company is using Amazon ElastiCache for Redis as a caching layer in front of an Amazon Aurora MySQL database. The application is experiencing higher latency than expected. Which database design pattern should the specialist recommend to improve read performance?

Accepted Answer

Use Aurora Replicas to offload read traffic from the primary instance.. Option B is correct. Adding Aurora Replicas to distribute read traffic improves read performance and reduces load on the primary. Option A is wrong because DAX is for DynamoDB, not Aurora. Option C is wrong because increasing cache size may not help if cache misses are not the issue. Option D is wrong because read replicas in ElastiCache are already used; the issue is the database.

Answer

Increase the ElastiCache cluster size to accommodate more data.

Answer

Enable Multi-AZ on the ElastiCache cluster and use read replicas.

Answer

Implement Amazon DynamoDB Accelerator (DAX) in front of Aurora.

Question 3

A database specialist needs to monitor the resource utilization of Amazon RDS DB instances. Which AWS service provides OS-level metrics such as memory, disk, and CPU usage?

Accepted Answer

Amazon RDS Enhanced Monitoring. Option B is correct. Enhanced Monitoring provides OS-level metrics for RDS instances. Option A is wrong because Performance Insights provides database performance metrics, not OS metrics. Option C is wrong because CloudWatch provides hypervisor-level metrics, not OS metrics. Option D is wrong because CloudTrail logs API calls.

Answer

Amazon RDS Performance Insights

Answer

Amazon CloudWatch

Answer

AWS CloudTrail

Question 4

A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. Which TWO methods can the database specialist use to minimize downtime during the migration?

Accepted Answer

Use Oracle GoldenGate to replicate data continuously.. Options B and D are correct. AWS DMS with ongoing replication (B) and Oracle GoldenGate (D) both support near-zero downtime migration. Option A is wrong because exporting/importing causes downtime. Option C is wrong because RMAN is not directly supported for RDS. Option E is wrong because a backup/restore causes downtime.

Answer

Use Oracle Recovery Manager (RMAN) to back up and restore.

Answer

Take a full database backup and restore to RDS.

Answer

Use Oracle Data Pump to export and import the database.

Question 5

A database specialist is troubleshooting a performance issue on an Amazon Aurora MySQL DB cluster. The cluster has a primary instance and two Aurora Replicas. The application is experiencing high read latency. Which THREE actions should the specialist take to identify the cause?

Accepted Answer

Check the Performance Insights for the Aurora Replicas to identify long-running queries.. Options A, B, and D are correct. Monitoring ReplicaLag (A), checking for long-running queries on replicas (B), and evaluating Connection Count metrics (D) help identify read latency causes. Option C is wrong because write latency is not the issue. Option E is wrong because increasing instance size is a remedy, not a diagnostic step.

Answer

Check the Write Latency metric on the primary instance.

Answer

Increase the instance size of the Aurora Replicas.

Question 6

A company is using Amazon DynamoDB with Auto Scaling enabled. The database specialist notices that write traffic is being throttled occasionally. Which TWO factors could cause throttling despite Auto Scaling?

Accepted Answer

The write traffic exceeds the maximum provisioned capacity that was set for Auto Scaling.. Options A and D are correct. Hot partitions (A) can cause throttling even with Auto Scaling because a single partition can exceed its limit. Throttling due to exceeding the maximum provisioned capacity (D) can also occur. Option B is wrong because Global Tables replicate writes but do not cause throttling. Option C is wrong because Auto Scaling is disabled? (the question says enabled, so C is irrelevant). Option E is wrong because DAX is for reads.

Answer

The table has Global Tables enabled, causing cross-region replication overhead.

Answer

Auto Scaling is not configured to scale up quickly enough for sudden traffic spikes.

Answer

DynamoDB Accelerator (DAX) is not caching write operations.

Question 7

A database specialist sees the above output for an RDS MySQL instance. The application reports that the instance is not accepting writes. What is the most likely cause?

Accepted Answer

The instance is a read replica and cannot accept write requests.. Option B is correct. The output shows the instance is a read replica (ReadReplicaSourceDBInstanceIdentifier is set), which means it is read-only and cannot accept writes. Option A is wrong because Multi-AZ does not affect write capability. Option C is wrong because storage encryption does not prevent writes. Option D is wrong because insufficient IOPS would not make it read-only.

Answer

The allocated IOPS are insufficient for the write workload.

Answer

Multi-AZ is not enabled, so the instance cannot accept writes.

Answer

Storage encryption is enabled, which prevents write operations.

Question 8

A database specialist created the above IAM policy for a user. When the user attempts to delete an item from the Orders table, what happens?

Accepted Answer

The user cannot delete items because the Deny statement takes precedence.. Option C is correct. The explicit Deny overrides the Allow, so the user cannot delete items. Option A is wrong because Deny takes precedence. Option B is wrong because the Deny explicitly restricts deletion. Option D is wrong because the policy explicitly denies deletion.

Answer

The user cannot delete items because the policy does not include a condition.

Answer

The user can delete items because the Allow statement grants permission.

Answer

The user can delete items only if they have another policy that allows it.

Question 9

A database specialist sees the above error in the application logs for an Amazon RDS for MySQL DB instance. The application is a web server running on an EC2 instance. What is the most likely cause?

Accepted Answer

The database connection timed out due to inactivity or network connectivity issues.. Option A is correct. The error 'MySQL server has gone away' typically occurs when the connection to the database is closed, often due to a timeout or network issue. Option B is wrong because it is a connection error, not a query execution error. Option C is wrong because disk space issues cause different errors. Option D is wrong because authentication errors are different.

Answer

The database user password has expired.

Answer

A user attempted to execute an invalid SQL query.

Answer

The database instance has run out of disk space.

Question 10

A company is running an Amazon RDS for MySQL DB instance. The database performance has degraded over time. The DBA suspects that the issue is due to a high number of connections that are in a 'sleep' state from a legacy application. What is the MOST effective solution to automatically terminate idle connections?

Accepted Answer

Modify the 'wait_timeout' parameter in the DB parameter group to a lower value.. Option C is correct because Amazon RDS for MySQL supports the 'wait_timeout' parameter, which automatically closes idle connections after the specified number of seconds. Reducing this value from the default 28800 seconds will terminate sleeping connections sooner. Option A is incorrect because manually killing connections is not automated. Option B is incorrect because RDS Proxy does not terminate idle connections; it manages connection pooling. Option D is incorrect because modifying 'max_connections' does not affect idle connections.

Answer

Increase the 'max_connections' parameter to accommodate more idle connections.

Answer

Enable Amazon RDS Proxy to manage connection pooling and automatically close idle connections.

Answer

Use a script to run 'SHOW PROCESSLIST' and manually kill idle connections.

Question 11

A SysOps administrator is tasked with monitoring the free storage space on all Amazon RDS DB instances. Which AWS service should be used to set up an alarm that sends an email notification when free storage space falls below a threshold?

Accepted Answer

Amazon CloudWatch with an alarm on the FreeStorageSpace metric and an SNS topic.. Option A is correct because Amazon CloudWatch can monitor RDS metrics such as 'FreeStorageSpace' and trigger an alarm that sends a notification via Amazon SNS. Option B is incorrect because AWS CloudTrail is for auditing API calls. Option C is incorrect because AWS Config tracks resource configuration changes. Option D is incorrect because Amazon Inspector is for security assessments.

Answer

AWS CloudTrail to monitor storage events.

Answer

AWS Config to track storage configuration changes.

Answer

Amazon Inspector to check for storage vulnerabilities.

Question 12

A company has a production Amazon DynamoDB table with on-demand capacity. The table experiences occasional throttling due to hot partitions. The operations team wants to implement a solution to identify the specific partition keys causing the throttling. What is the MOST efficient approach?

Accepted Answer

Enable Amazon CloudWatch Contributor Insights for DynamoDB.. Option D is correct because Amazon CloudWatch Contributor Insights can analyze DynamoDB logs and identify the most accessed partition keys, helping to pinpoint hot partitions. Option A is incorrect because CloudWatch Logs Insights requires enabling VPC Flow Logs, which is not specific to DynamoDB. Option B is incorrect because AWS X-Ray traces requests but does not provide partition-level metrics. Option C is incorrect because DynamoDB Streams capture changes, not access patterns.

Answer

Enable AWS X-Ray tracing on the application and analyze traces.

Answer

Enable VPC Flow Logs and use CloudWatch Logs Insights to query the logs.

Answer

Enable DynamoDB Streams and process the stream records to identify hot keys.

Question 13

A data engineer is troubleshooting a slow-running query on an Amazon Redshift cluster. The query involves large table joins and aggregations. Which diagnostic step should be taken FIRST to understand the query execution plan and identify bottlenecks?

Accepted Answer

Run the EXPLAIN command on the query to review the execution plan.. Option B is correct because the EXPLAIN command shows the query execution plan, including join types, distribution styles, and sort keys, which helps identify bottlenecks. Option A is incorrect because STL_QUERY logs completed queries but does not provide the plan. Option C is incorrect because SVV_TABLE_INFO gives table statistics, not the query plan. Option D is incorrect because WLM metrics show queue performance, not individual query plans.

Answer

Monitor the WLM queue metrics for the query.

Answer

Check the SVV_TABLE_INFO view for table distribution and sort keys.

Answer

Query the STL_QUERY system table to review the query text.

Question 14

A company runs an Amazon Aurora MySQL DB cluster with one writer and two readers. The application experiences increased read latency. The DBA wants to offload read traffic from the writer instance. Which configuration change should be made to the application?

Accepted Answer

Modify the application to use the reader endpoint for read queries.. Option A is correct because the application should connect to the reader endpoint to distribute read queries across the read replicas. Option B is incorrect because the cluster endpoint points to the writer. Option C is incorrect because the instance endpoint is for a specific instance. Option D is incorrect because a custom endpoint is used for specific reader groups, but the standard reader endpoint is simpler for general offloading.

Answer

Modify the application to use an individual instance endpoint for each reader.

Answer

Create a custom endpoint that includes both writer and readers.

Answer

Modify the application to use the cluster endpoint for all queries.

Question 15

A database administrator is using AWS DMS to migrate an on-premises Oracle database to Amazon RDS for PostgreSQL. The migration has been running for several hours, but the full load phase is taking much longer than expected. The CPU utilization on the DMS replication instance is consistently below 10%. What is the MOST likely cause of the slow performance?

Accepted Answer

The target RDS instance is throttling write operations due to low IOPS.. Option C is correct because when migrating to a target with limited write capacity (e.g., RDS instance with low IOPS), DMS may be throttled by the target's write throughput, while the replication instance itself is underutilized. Option A is incorrect because DMS can use multiple tasks, but the issue is not about parallelism. Option B is incorrect because DMS uses its own engine, not PostgreSQL. Option D is incorrect because using LOBs can slow down migration, but the symptom is low CPU on the replication instance, not high.

Answer

The source database has large LOBs that are being transferred in full LOB mode.

Answer

The target database engine is not compatible with DMS.

Answer

The DMS task is not configured to use parallel tables.