OEM export fails!

Hi all!

Query:

Working on Oraclev8i 8.1.6.0.0 with OS as NT.

1.Say I have to calculate the Avg.Row Length and Avg.Column Length of USER_CONS_COLUMNS
Table as under:

How should I calculate it to fix the correct BLOCK SIZE in order to avoid
Row migration and Row Chaining:

SQL> desc USER_CONS_COLUMNS
Name Null? Type
----------------------------------------- -------- ----------------------------
OWNER NOT NULL VARCHAR2(30)
CONSTRAINT_NAME NOT NULL VARCHAR2(30)
TABLE_NAME NOT NULL VARCHAR2(30)
COLUMN_NAME VARCHAR2(4000)
POSITION NUMBER

2.I have created few users and those users would like to access the view USER_CONS_COLUMNS
under Balaji schema.Is it possible!.

The above users do not possess any schema objects.

How could I grant them select on BALAJI.USER_CONS_COLUMNS view so that the users from
their login ID would be able to view all the column_name,constraint_names of Balaji schema's
tables.

Provided that all the DB tables have been created in BALAJI schema and the users created
as above just have connect,resource,select,update,delete privileges
on Balaji.Table_names with them!

3.I am receiving the following error as under:

Connected to OEM : SYSMAN/PWD@biac-04
where biac-04 being the management server.

Conected to DB : SYSTEM/PWD@DB as SYSDBA.

Whenever I perform Export from OEM I get error status:failed!

Could you please let me know as to where I had goen wrong!

Thanks & Regards,

Amit.