Unclean shutdown resets all statistics counters losing historical data

After an unclean shutdown (immediate shutdown, server crash, starting from base backup, or point-in-time recovery), all cumulative statistics counters are reset to zero, losing historical performance data that was not persisted to pg_stat subdirectory.

After unclean shutdown events, document the statistics reset timestamp. Re-establish baseline metrics. Consider more frequent clean shutdowns or checkpoint intervals to preserve statistics. Monitor for crash recovery events that trigger resets.