Add recovery for 'real WAL only'.

doc/NOTES.md

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+NOTES
+=====
+
+## RECOVERY
+
+### REAL WAL EXISTS, SHADOW EXISTS
+
+Scenario: Unclean close by application process.
+
+Action: Verify last page from both match.
+
+
+### REAL WAL DOESN'T EXISTS, SHADOW EXISTS
+
+Scenario: Application closed cleanly & removed WAL.
+
+Action: Verify last page of shadow matches database page.
+
+
+### REAL WAL EXISTS, SHADOW DOESN'T EXIST
+
+Scenario: Application wrote WAL; system crashed before shadow written/sync'd.
+
+Action: Start new generation. 
+
+
+### REAL WAL DOESN'T EXIST, SHADOW DOESN'T EXIST
+
+Scenario: No writes have occurred since the DB was switched to WAL mode.
+
+Action: Nothing to recover. Wait for first WAL write.
+