## staking
 
 bondingDuration: `u32`
- **interface**: `staking.bondingDuration`
- **summary**:    Number of eras that staked funds must remain bonded for. 
 
 historyDepth: `u32`
- **interface**: `staking.historyDepth`
- **summary**:    Number of eras to keep in history. 

   Following information is kept for eras in `[current_era -  HistoryDepth, current_era]`: `ErasStakers`, `ErasStakersClipped`,  `ErasValidatorPrefs`, `ErasValidatorReward`, `ErasRewardPoints`,  `ErasTotalStake`, `ErasStartSessionIndex`, `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. 

   Note: `HistoryDepth` is used as the upper bound for the `BoundedVec`  item `StakingLedger.legacy_claimed_rewards`. Setting this value lower than  the existing value can lead to inconsistencies in the  `StakingLedger` and will need to be handled properly in a migration.  The test `reducing_history_depth_abrupt` shows this effect. 
 
 maxExposurePageSize: `u32`
- **interface**: `staking.maxExposurePageSize`
- **summary**:    The maximum size of each `T::ExposurePage`. 

   An `ExposurePage` is weakly bounded to a maximum of `MaxExposurePageSize`  nominators. 

   For older non-paged exposure, a reward payout was restricted to the top  `MaxExposurePageSize` nominators. This is to limit the i/o cost for the  nominator payout. 

   Note: `MaxExposurePageSize` is used to bound `ClaimedRewards` and is unsafe to reduce  without handling it in a migration. 
 
 maxUnlockingChunks: `u32`
- **interface**: `staking.maxUnlockingChunks`
- **summary**:    The maximum number of `unlocking` chunks a [`StakingLedger`] can  have. Effectively determines how many unique eras a staker may be  unbonding in. 

   Note: `MaxUnlockingChunks` is used as the upper bound for the  `BoundedVec` item `StakingLedger.unlocking`. Setting this value  lower than the existing value can lead to inconsistencies in the  `StakingLedger` and will need to be handled properly in a runtime  migration. The test `reducing_max_unlocking_chunks_abrupt` shows  this effect. 
 
 sessionsPerEra: `u32`
- **interface**: `staking.sessionsPerEra`
- **summary**:    Number of sessions per era. 
 
 slashDeferDuration: `u32`
- **interface**: `staking.slashDeferDuration`
- **summary**:    Number of eras that slashes are deferred by, after computation. 

   This should be less than the bonding duration. Set to 0 if slashes  should be applied immediately, without opportunity for intervention.