dbms_metadata()

Users:
set pages 0 echo off termout off long 9999999 verify off feedback off
exec DBMS_METADATA.SET_TRANSFORM_PARAM(DBMS_METADATA.SESSION_TRANSFORM,'SQLTERMINATOR',true);
SELECT DBMS_METADATA.GET_DDL('USER', USERNAME)
FROM DBA_USERS u
where u.username in (select username from dba_users
where username not in ('SYS','SYSTEM','OUTLN','DBSNMP'))
UNION ALL
SELECT DBMS_METADATA.GET_DDL('ROLE', ROLE)
FROM DBA_ROLES
UNION ALL
SELECT DBMS_METADATA.GET_GRANTED_DDL('ROLE_GRANT', USERNAME)
from dba_users u
where u.username in (select username from dba_users
where username not in ('SYS','SYSTEM','OUTLN','DBSNMP'))
and exists (select 'x' from dba_role_privs drp where drp.grantee = u.username)
UNION ALL
SELECT DBMS_METADATA.GET_GRANTED_DDL('SYSTEM_GRANT', USERNAME)
FROM DBA_USERS u
where u.username in (select username from dba_users
where username not in ('SYS','SYSTEM','OUTLN','DBSNMP'))
and exists (select 'x' from dba_sys_privs dsp where dsp.grantee = u.username);
DB Links:
SELECT DBMS_METADATA.GET_DDL('DB_LINK',a.db_link,a.owner) FROM all_db_links a;
Tablespace:
SELECT DBMS_METADATA.GET_DDL('TABLESPACE', TABLESPACE_NAME) FROM DBA_TABLESPACES;