private void removeVariables() {
      remove(VARIABLES_PREFIX, CHAIN_HEAD_HASH.getBytes());
      remove(VARIABLES_PREFIX, FINALIZED_BLOCK_HASH.getBytes());
      remove(VARIABLES_PREFIX, SAFE_BLOCK_HASH.getBytes());
      remove(VARIABLES_PREFIX, FORK_HEADS.getBytes());
      remove(Bytes.EMPTY, SEQ_NO_STORE.getBytes());
    }
One time migration of variables from the blockchain storage to the dedicated variable storage.
To avoid state inconsistency in case of a downgrade done without running the storage
revert-variables subcommand it fails giving the possibility to retry the downgrade procedure.
ethereum/core/src/main/java/org/hyperledger/besu/ethereum/storage/keyvalue/KeyValueStoragePrefixedKeyBlockchainStorage.java