github.com/Finschia/finschia-sdk@v0.48.1/x/staking/spec/04_begin_block.md (about)

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     5  # Begin-Block
     6  
     7  Each abci begin block call, the historical info will get stored and pruned
     8  according to the `HistoricalEntries` parameter.
     9  
    10  ## Historical Info Tracking
    11  
    12  If the `HistoricalEntries` parameter is 0, then the `BeginBlock` performs a no-op.
    13  
    14  Otherwise, the latest historical info is stored under the key `historicalInfoKey|height`, while any entries older than `height - HistoricalEntries` is deleted.
    15  In most cases, this results in a single entry being pruned per block.
    16  However, if the parameter `HistoricalEntries` has changed to a lower value there will be multiple entries in the store that must be pruned.