Oracle: Can a user log in without a password?
Possible solutions:


Use a Secure External Password Store (Oracle Wallet): http://docs.oracle.com/database/121/DBSEG/authentication.htm#CHDHGAIJ


You can use the stored credentials without specifying a username or password. Connection string: /@orcl.


REMOTE_OS_AUTHENT: http://docs.oracle.com/cd/E18283_01/server.112/e17110/initparams208.htm


Not recommended, insecure, mentioned just for completeness, do not use it.


Kerberos Authentication: http://docs.oracle.com/database/121/DBSEG/asokerb.htm


You can use your directory credentials for logging in without specifying your username or password. Connection string: /@orcl.


SSL Authentication: http://docs.oracle.com/database/121/DBSEG/asossl.htm


You own a certificate and you will be authenticated by that, without specifying a username or password. Connection string: /@orcl.


Operating system authentication based on group membership. Works only locally, and for privileged users. Connection string: / as sysdba, / as sysoper, / as sysbackup, / as sysdg, / as syskb.