Following information is kept for eras in [current_era - HistoryDepth, current_era]: ErasValidatorPrefs, ErasValidatorReward,
ErasRewardPoints, ErasTotalStake, ClaimedRewards,
ErasStakersPaged, ErasStakersOverview.
Must be more than the number of eras delayed by session.
I.e. active era must always be in history. I.e. active_era > current_era - history_depth must be guaranteed.
If migrating an existing pallet from storage value to config value,
this should be set to same value or greater as in storage.
Number of eras to keep in history.
Following information is kept for eras in
[current_era - HistoryDepth, current_era]:ErasValidatorPrefs,ErasValidatorReward,ErasRewardPoints,ErasTotalStake,ClaimedRewards,ErasStakersPaged,ErasStakersOverview.Must be more than the number of eras delayed by session. I.e. active era must always be in history. I.e.
active_era > current_era - history_depthmust be guaranteed.If migrating an existing pallet from storage value to config value, this should be set to same value or greater as in storage.