DBA

There is two method to connect sysdba user :-

with password

without password

sql> conn / as sysdba ------ without password

* Oracle database user must have sysdba privileges.
* Os user must add in dba group.
* In sqlnet.ora file must content "NTS" in below line

sqlnet.authentication_services = (NTS)
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with password

sql>conn sys/pwd as sysdba ------- with password

prevent to connect without password.
* remove os user from dba group.
* edit sqlnet.ora file and change "none" to "nts" in below line.
sqlnet.authentication_services =(none)
Default value is nts when sqlnet.ora file created.
***************************** DBA ******************