A Time Machine is a core construct of the copy data management service in NDB that captures and manages the data of a database to deliver a recovery point objective (RPO) SLA. A Time Machine can enter a Frozen state for various reasons, such as database de-registration, snapshot or log catchup failures, or manual intervention. When a Time Machine is in a Frozen state, it stops taking new snapshots and log backups, and cannot perform any clone, refresh, or restore operations. To resume the normal operation of a Time Machine, it must be thawed by resolving the root cause of the freeze. One of the common causes of a Time Machine freeze is when the database is de-registered from NDB without removing the Time Machine. This can happen when the administrator wants to move the database to a different NDB instance or cluster, or when the database is accidentally de-registered. In this case, the Time Machine becomes orphaned and frozen, and cannot be used for any operations. To complete the request to refresh a database clone from a new manual snapshot, the administrator must first re-register the database in NDB using the same database name and ID as before. This will automatically thaw the Time Machine and resume its operation. The administrator can then create a new manual snapshot from the Time Machine and use it to refresh the database clone. The other options are not correct, as they either require unnecessary steps or do not address the root cause of the freeze. References:
Nutanix Certified Professional - Database Automation (NCP-DB) v6.5, Section 5 - Protect NDB-managed Databases Using Time Machine, Objective 5.1: Create, delete, and modify SLA retention policies
Nutanix Database Management & Automation (NDMA) Course, Module 4: Nutanix Database Service (NDB) Data Protection, Lesson 4.1: Data Protection Overview, Topic: Time Machine Concepts
Nutanix Support & Insights, TN-2101: Nutanix Database Service Time Machine Under the Hood, Section: Time Machine States and Transitions
