Differences between sysdba, sysoper, normal, sys, sysdba, and DBA

1. Differences between sys and system users
System users can only log on to Em as normal users.
The sys user has the "sysdba" or "sysoper" permissions, and can only use these two identities to log on to Em, but cannot use normal.
"Sysoper" permission, that is, database operator permission, includes:
Open Database Server close Database Server
Backup database recovery database
Log archiving session restrictions
The "sysdba" permission, that is, the database administrator permission, includes:
Open Database Server close Database Server
Backup database recovery database
Log archiving session restrictions
Manage functions to create databases

2. Differences between normal, sysdba, and sysoper
Normal is a common user and can operate the database only after being authorized by sys.
Sysdba has the highest system Permissions
Sysoper is mainly used to start and close databases. After logging on to sysoper, the user is public.
After logging on to sysdba, It is sys, and only sys can log on to sysdba.

SQL> Conn/As sysdba
Connected.
SQL> grant sysoper to test;

Authorization successful.

SQL> conn test/test as sysoper;
Connected.
SQL> show user
The user is "public"
SQL> conn test/test as sysdba
Connected.
SQL> show user
User is "sys"
SQL>

Differences between dBA and sysdba
What are the differences between dBA and sysdba system roles?
Before explaining this, I need to talk about the Oracle service creation process.
· Create an instance
· Start an instance
· Create a database (system tablespace is required)
Startup Process
· Instance startup
· Load databases
· Open a database

Sysdba manages Oracle instances and does not rely on the full startup of the entire database,
Once the instance is started, it already exists. you can log on to the instance as sysdba, load the database, and open the database.
Only when the database is opened, or the entire database is fully started, the DBA role has a foundation. DBA is only a role.