I login as a user which has SYS privilege and ran below sql to check some of session variables so far everything looks good and expected.

select substr(user,1,5) as "user", substr(sys_context('USERENV','SESSION_USER'),1,5) as SESSION_USER, substr(sys_context('USERENV','CURRENT_SCHEMA'),1,5) as CURRENT_SCHEMA
        , substr(sys_context('USERENV','CURRENT_USER'),1,5) as CURRENT_USER, sys_context('USERENV','CURRENT_SCHEMAID') as CURRENT_SCHEMAID
from dual;

user  SESSI CURRE CURRE CURRENT_SCHEMAID                                                                                                                                                                                                                                                
----- ----- ----- ----- -----------------
SYS   SYS   SYS   SYS   0                                                                                                                                                                                                                                                               

Now connect as different user and run same SQL it still show SYS I expect to see tst is this expected?

conn tst/tst


select substr(user,1,5) as "user", substr(sys_context('USERENV','SESSION_USER'),1,5) as SESSION_USER, substr(sys_context('USERENV','CURRENT_SCHEMA'),1,5) as CURRENT_SCHEMA
        , substr(sys_context('USERENV','CURRENT_USER'),1,5) as CURRENT_USER, sys_context('USERENV','CURRENT_SCHEMAID') as CURRENT_SCHEMAID
from dual;

user  SESSI CURRE CURRE CURRENT_SCHEMAID                                                                                                                                                                                                                                                
----- ----- ----- ----- -----------------
SYS   SYS   SYS   SYS   0 

thanks in advance for your time.

SQL> select substr(user,1,5) as "user",
  2         substr(sys_context('USERENV','SESSION_USER'),1,5) as SESSION_USER,
  3         substr(sys_context('USERENV','CURRENT_SCHEMA'),1,5) as CURRENT_SCHEMA ,
  4         substr(sys_context('USERENV','CURRENT_USER'),1,5) as CURRENT_USER,
  5         sys_context('USERENV','CURRENT_SCHEMAID') as CURRENT_SCHEMAID
  6  from dual;

user                 SESSION_USER         CURRENT_SCHEMA       CURRENT_USER         CURRENT_SCHEMAID
-------------------- -------------------- -------------------- -------------------- --------------------
SYS                  SYS                  SYS                  SYS                  0

SQL> conn scott/tiger
Connected.
SQL> select substr(user,1,5) as "user",
  2         substr(sys_context('USERENV','SESSION_USER'),1,5) as SESSION_USER,
  3         substr(sys_context('USERENV','CURRENT_SCHEMA'),1,5) as CURRENT_SCHEMA ,
  4         substr(sys_context('USERENV','CURRENT_USER'),1,5) as CURRENT_USER,
  5         sys_context('USERENV','CURRENT_SCHEMAID') as CURRENT_SCHEMAID
  6  from dual;

user                 SESSION_USER         CURRENT_SCHEMA       CURRENT_USER         CURRENT_SCHEMAID
-------------------- -------------------- -------------------- -------------------- --------------------
SCOTT                SCOTT                SCOTT                SCOTT                127