How to Check ORACLE_HOME from the Database

First Method:

select NVL(substr(file_spec, 1, instr(file_spec, '\', -1, 2) -1) , substr(file_spec, 1, instr(file_spec, '/', -1, 2) -1)) folder
from dba_libraries
where library_name = 'DBMS_SUMADV_LIB'

2nd Method (Requires priv to run sys.dbms_system) :

DECLARE

folder VARCHAR2(100);

BEGIN

sys.dbms_system.get_env('ORACLE_HOME', folder);
dbms_output.put_line(folder);

END;