SELECT  free.tablespace_name TABLESPACE, 
    ROUND(files.bytes / 1073741824, 2) gb_total,
    ROUND((files.bytes - free.bytes)  / 1073741824, 2) gb_used,      
    ROUND(free.bytes  / files.bytes * 100) || '%' "%FREE" 
FROM
  (
    SELECT tablespace_name, SUM(bytes) bytes FROM dba_free_space
    GROUP BY tablespace_name
  ) free,
  (
    SELECT tablespace_name, SUM(bytes) bytes FROM dba_data_files 
    GROUP BY tablespace_name
  ) files
WHERE 
  free.tablespace_name = files.tablespace_name;

declare
base_link VARCHAR2(200);

begin
for base_link in (Select DB_LINK from USER_DB_LINKS)
  loop
    insert into LIST_DBLINKS(NAME_link) values base_link;
    
    end loop;
    commit;


end;  
/

declare
base_link VARCHAR2(200);

begin
for base_link in (Select DB_LINK  from USER_DB_LINKS)
  loop
    
   execute immediate 'select name from v$database@' || base_link ||;
    
    end loop;
    
end;  
/