The session index at which the era start for the last [Config::HistoryDepth] eras.
Config::HistoryDepth
Note: This tracks the starting session (i.e. session index when era start being active) for the eras in [CurrentEra - HISTORY_DEPTH, CurrentEra].
[CurrentEra - HISTORY_DEPTH, CurrentEra]
The session index at which the era start for the last [
Config::HistoryDepth] eras.Note: This tracks the starting session (i.e. session index when era start being active) for the eras in
[CurrentEra - HISTORY_DEPTH, CurrentEra].