Before patching several Nutanix database server VMs using the "Patch OS now" feature in NDB, the administrator must configure a Repository. A repository (e.g., a custom patch repository or Nutanix-provided source) contains the OS updates or patches (e.g., for Windows or Red Hat-based systems). NDB requires this repository to be specified to fetch and apply the patches, ensuring the database VMs are updated from a validated source.

Other options are unrelated to patching:

B. Active Directory Access: Used for authentication, not patching.

C. pulse: Refers to Nutanix Pulse for support, not patch configuration.

D. An SMTP Server: Configured for alerts, not patching.

Thus, the verified answer is A, reflecting the patching prerequisite.

Official Nutanix Database Automation References

Nutanix Database Management & Automation (NDMA) course, Module 6: Maintenance and Patching, Lesson 6.3: Creating Maintenance Plans.

Nutanix Certified Professional - Database Automation (NCP-DB) v6.5 Knowledge Objectives, Section 6: Optimize NDB Solutions, Objective 6.3: Manage Maintenance Plans (applicable to v6.10).

Nutanix NDB Administration Guide: "Configuring Patch Repositories" section.