If Oracle wallet is enabled in your
oracle database and if you forget to enable the wallet after opening the database
you will get following error.
ORA-28365: wallet is not open
In case if you try to access RMAN
backup you will get following error message
ORA-19913: unable to decrypt backup
ORA-28365: wallet is not open
There is one data dictionary view v$encryption_wallet for the same to check.