Granting SYSDBA privileges to a user

Scenario: I have the DBA role and am able to connect as SYSDBA, but I am not able to connect as SYSOPER:

SQL> connect pubs/pubs
 Connected.
SQL> drop user tom; 

User dropped. 

SQL> create user tom identified by ton1234; 
User created. 

SQL> grant dba to tom
SQL> connect tom/tom1234 as sysdba;
 Connected.
 
SQL> connect tom/tom1234 as sysoper;
ERROR:
ORA-01031: insufficient privileges 

Warning: You are no longer connected to ORACLE.
 SQL> 
SQL> connect pubs/pubs;
Connected.
SQL> 
SQL> grant sysoper to tom;
grant sysoper to tom
 *
ERROR at line 1:
ORA-01031: insufficient privileges 

SQL> 
SQL> connect tom/tom1234 as sysoper;
ERROR:
ORA-01031: insufficient privileges

Question: What is the difference between the dba roles

1. sysdba system privilege and
2. sysoper system privilege?

Answer: The DBA role does not include the SYSDBA or SYSOPER system privileges.
The SYSDBA and SYSOPER are special administrative privileges that allow an administrator to perform basic database administration tasks, such as

1. creating the database,
2. instance startup and shutdown,
3. drop a database,
4. open and mount a database, or
5. place database in archivelog mode.