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STATUS_FLT_INSTANCE_ALTITUDE_COLLISION
An altitude identifies a minifilter instance's position in the volume stack, and only one instance can occupy a particular altitude on a given volume. This status is therefore an ordering collision, not a generic access-denied condition.
Inspect the installed instance configuration and the actual stack before changing an altitude. Changing it casually can alter pre-operation and post-operation ordering relative to security, encryption, backup, or reparse filters. When the collision comes from an explicit attach, also verify whether an existing automatic instance already performs the intended work.
Useful distinction
- Altitude collision: the stack position is already occupied.
- Instance name collision: an identifier is already in use.
- Filter not ready: the filter has not yet begun filtering at all.
FltAttachVolumeAtAltitude | Filter Manager concepts | NTSTATUS reference
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