DBS-C01 Deployment and Migration Practice Question
A company is migrating a 2 TB Oracle database from on-premises to Amazon RDS for Oracle using AWS DMS. The migration completes successfully, but the new RDS instance shows higher CPU utilization than the on-premises database for the same workload. Which action is MOST likely to reduce CPU utilization on RDS?
⚠ Common exam trap
The trap is assuming that CPU utilization is always due to compute limits and overlooking the impact of I/O wait. Candidates may also incorrectly believe Oracle Multitenant reduces CPU, but it actually adds overhead and is not applicable to existing RDS instances.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Increase the allocated storage to improve IOPS
Increasing allocated storage on Amazon RDS for Oracle directly improves the provisioned IOPS (if using Provisioned IOPS) or baseline IOPS (for gp2/gp3). Higher IOPS reduces I/O wait time, which is a common cause of high CPU utilization when the database is I/O-bound. Query optimization or instance resizing may also help, but increasing storage is a simple, low-risk action that often alleviates I/O-related CPU pressure. Option B is incorrect because Oracle Multitenant (CDB/PDB) architecture adds container management overhead and is not designed to reduce CPU utilization; also, converting an existing non-CDB RDS instance to CDB is not supported.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Disable automated backups to free resources
Why it's wrong here
Disabling automated backups may free some I/O and CPU resources, but the savings are minimal and not the most effective action for reducing CPU utilization in this scenario.
- ✗
Enable Oracle Multitenant architecture
Why it's wrong here
Enabling Oracle Multitenant architecture typically increases CPU overhead due to container management processes and is not a supported or effective way to reduce CPU utilization. RDS also does not allow conversion from non-CDB to CDB after instance creation.
- ✓
Increase the allocated storage to improve IOPS
Why this is correct
Increasing allocated storage improves IOPS, which reduces I/O wait times and can significantly lower CPU utilization if the database is I/O-bound. This is often the most straightforward first step.
- ✗
Change the RDS instance to a burstable class
Why it's wrong here
Changing to a burstable instance class (e.g., db.t3) may reduce CPU costs but can lead to CPU credit exhaustion under sustained load, potentially worsening performance and increasing CPU utilization.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
Go deeper
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