-- any object owned by sys by default(created when database is created) is not exported.
-- but u can create a base table and do the export
-- but, ORACLE HIGHLY RECOMENDS NOT TO HAVE ANY CUSTOM OBJECTS IN SYS/SCHEMA.
-- so u can create the backup table as shown in another schema than SYS/SYSTEM. ( I HAVE USED SYS -- SCHEMA.DONT DO THAT.
-- 
-- but, WHAT IS WHOLE USE?
-- why is it required to backup the user_jobs?
-- 

Microsoft Windows 2000 [[Version 5.00.2195]]
(C) Copyright 1985-2000 Microsoft Corp.

C:>exp sys/sys tables=(dba_tables)

Export: Release 8.1.6.0.0 - Production on Thu Mar 6 07:46:42 2003

(c) Copyright 1999 Oracle Corporation.  All rights reserved.

Connected to: Oracle8i Enterprise Edition Release 8.1.6.0.0 - Production
With the Partitioning option
JServer Release 8.1.6.0.0 - Production
Export done in WE8ISO8859P1 character set and WE8ISO8859P1 NCHAR character set

About to export specified tables via Conventional Path ...
EXP-00011: SYS.DBA_TABLES does not exist
Export terminated successfully with warnings.

--
-- create a table...from the view
--

sys@itloaner1_local > create table backup_dba_tables as select * from dba_tables;

Table created.

sys@itloaner1_local > host

C:>exp sys/sys tables=(backup_dba_tables)

Export: Release 8.1.6.0.0 - Production on Thu Mar 6 07:49:05 2003

(c) Copyright 1999 Oracle Corporation.  All rights reserved.

Connected to: Oracle8i Enterprise Edition Release 8.1.6.0.0 - Production
With the Partitioning option
JServer Release 8.1.6.0.0 - Production
Export done in WE8ISO8859P1 character set and WE8ISO8859P1 NCHAR character set

About to export specified tables via Conventional Path ...
. . exporting table              BACKUP_DBA_TABLES        289 rows exported
Export terminated successfully without warnings.

C:>