Oracle SYS users cannot log on with the default password change_on_install (error code: ORA-28009)

When you log on to the database using the default Oracle SQL plus (for example,), you can use the System user's default password manager to log on to the database.

However, if you enter the user SYS and the default password change_on_install, you cannot log on.
The following error is reported:

Error:
ORA-28009: connection to SYS shoshould be as sysdba or sysoper

Problem Analysis:

Usage: conn [ect] [logon] [as {sysdba | sysoper}]
<Logon >::= <username> [/<password>] [@ <connect_string>] |/

If you log on as a sys user, you must log on in the full format !!

Solution:
1. Log On with the System user, and switch to the Sys user in the complete format: SQL> conn sys/change_on_install @ zgctwo as sysdba
Connected.

2. The host string on the logon interface is followed by the string as sysdba:

OK !! You can splice the connection string here.