When identifying which servers are no longer required, reviewing server CPU usage trends is the most helpful approach. Monitoring the CPU usage over time provides insights into how actively a server is being utilized.
Servers with consistently low CPU usage may be candidates for consolidation or decommissioning. By analyzing CPU utilization patterns, IT management can make informed decisions about which servers can be retired without impacting performance or availability1.
References:
1.
ISACA. "Technical Guide on IT Migration Audit." 1(http://kb.icai.org/pdfs/PDFFile5b278a12a66758.
27269499.pdf)
2. Zapier. "IT audit: The ultimate guide [with checklist]." 2(https://zapier.com/blog/it-audit/)
3. ISACA. "CISA Certification | Certified Information Systems Auditor." 3(https://www.isaca.org
/credentialing/cisa)

When reviewing an enterprise architecture (EA) department's decision to change a legacy system's components while maintaining its original functionality, an IS auditor should understand the current business capabilities delivered by the legacy system, as this would help to evaluate whether the change is justified, feasible, and aligned with the business goals and needs. The proposed network topology to be used by the redesigned system, the data flows between the components to be used by the redesigned system, and the database entity relationships within the legacy system are technical details that are less relevant for an IS auditor to understand when reviewing this decision. References: CISA Review Manual (Digital Version), Chapter 3, Section 3.2

Comprehensive and Detailed Step-by-Step Explanation:
To ensure that aservice vendor maintains required control levels, direct verification throughonsite assessmentsis the most effective approach.
* Option A (Correct):Onsite assessmentsallow auditors todirectly reviewcontrols, procedures, and evidence of compliancein real time, ensuring that service levels are being met.
* Option B (Incorrect):Unannounced vulnerability assessments may violatecontractual agreementsand ethical considerations.
* Option C (Incorrect):Reviewing theSLAensures agreement terms are clear but doesnot verify actual compliance.
* Option D (Incorrect):AControl Self-Assessment (CSA)is useful but relies onvendor-provided information, which may be biased or incomplete.
Reference:ISACA CISA Review Manual -Domain 4: Information Systems Operations and Business Resilience- Covers third-party risk management and audit approaches.