This is a view in the mssqlsystemresource database. The view indicates the state of mirrors.
mirroring_guid
uniqueidentifier
state_machine_name
nvarchar(120)
action_type
name
current_state
action_sequence
int
CREATE VIEW sys.dm_db_mirroring_past_actions AS SELECT * FROM OpenRowSet(TABLE DBMIRROR_PAST_ACTIONS)