Wallet v3.1.0-win64 began to issue such an error, please help understand ..
2019-01-24 05:42:19 *** System error while flushing: CDB : Error -30974, can't open database
2019-01-24 05:42:21 CDBEnv::EnvShutdown : Error -30974 shutting down database environment: DB_RUNRECOVERY: Fatal error, run database recovery
2019-01-24 05:42:21 Shutdown: done
v3.1.2 does not start at all

Wallet has been killed, sometimes windows updates do it when rebooting the system and doesn't wait for graceful shutdown to complete. Please restore the wallet.dat from a backup in backups/ folder.