What is SafeMode Ratcheting?: SafeMode is Purity's "immutability" feature that prevents snapshots from being deleted, eradicated, or modified, even by an administrator with compromised credentials. Ratcheting is the process of increasing the protection levels (like extending the retention period) for a protection group (pgroup) to ensure even stricter data safety.
The Dependency on Local Snapshots: SafeMode's primary function is to protect point-in-time copies of data residing on the array. For a protection group to be "ratcheted" into a SafeMode-protected state, it must have an active Local Snapshot Schedule.
Why Option C is the Constraint: If a protection group does not have a local snapshot schedule, there are no local snapshots being generated for SafeMode to "lock." SafeMode cannot protect what doesn't exist locally. While a pgroup might be used for replication only, SafeMode requires the local scheduling component to be active and configured to apply its immutable retention policies.
Why Option B is incorrect: Protection groups are designed to contain hosts, host groups, or volumes. This is the standard way to group related data for snapshot consistency and has no negative impact on SafeMode eligibility.
Operational Note: When you enable SafeMode on a protection group with a local schedule, the "Erradicate" button for those snapshots is disabled. To "ratchet" the protection, you typically work with Pure Storage Support to ensure the retention settings meet your compliance needs.