ORA-31693: Table data object "owner"."tablo" failed to load/unload and is being skipped due to error:
ORA-02354: error in exporting/importing data 
ORA-01555: snapshot too old: rollback segment number with name "" too small 
ORA-22924: snapshot too old

set serverout on
exec dbms_output.enable(100000);
declare
  pag    number;
  len    number;
  c      varchar2(10);
  charpp number := 8132/2;

begin
  for r in (select rowid rid, dbms_lob.getlength (<your_clob_column>) len
            from   <your_table_with_clcob_column>) loop
    if r.len is not null then
      for page in 0..r.len/charpp loop
        begin
          select dbms_lob.substr (<your_clob_column>, 1, 1+ (page * charpp))
          into   c
          from   <your_table_with_clcob_column> 
          where  rowid = r.rid;
        
        exception
          when others then
            dbms_output.put_line ('Error on rowid ' ||R.rid||' page '||page);
            dbms_output.put_line (sqlerrm);
        end;
      end loop;
    end if;
  end loop;
end;
/

CREATE TABLE "OWNER"."TABLO"
(
   "ID"       NUMBER NOT NULL ENABLE,
   "HEADER"   CLOB DEFAULT EMPTY_CLOB (),
   "BODY"     CLOB DEFAULT EMPTY_CLOB ()
)
SEGMENT CREATION IMMEDIATE
PCTFREE 10
PCTUSED 40
INITRANS 1
MAXTRANS 255
NOCOMPRESS
LOGGING
STORAGE (INITIAL 65536
         NEXT 1048576
         MINEXTENTS 1
         MAXEXTENTS 2147483645
         PCTINCREASE 0
         FREELISTS 1
         FREELIST GROUPS 1
         BUFFER_POOL DEFAULT
         FLASH_CACHE  DEFAULT
         CELL_FLASH_CACHE DEFAULT)
TABLESPACE "OWNER_DATA01"
LOB ("HEADER")
	STORE AS BASICFILE (TABLESPACE "OWNER_DATA01"
				ENABLE STORAGE IN ROW CHUNK 8192
				RETENTION
				NOCACHE
				LOGGING
				STORAGE(INITIAL 65536
					NEXT 1048576
					MINEXTENTS 1
					MAXEXTENTS 2147483645
					PCTINCREASE 0
					FREELISTS 1
					FREELIST GROUPS 1
					BUFFER_POOL DEFAULT
					FLASH_CACHE DEFAULT
					CELL_FLASH_CACHE DEFAULT
					)
				)
LOB ("BODY") 
	STORE AS BASICFILE (TABLESPACE "OWNER_DATA01"
				ENABLE STORAGE IN ROW CHUNK 8192
				RETENTION
				NOCACHE
				LOGGING
				STORAGE(INITIAL 65536
					NEXT 1048576
					MINEXTENTS 1
					MAXEXTENTS 2147483645
					PCTINCREASE 0
					FREELISTS 1
					FREELIST GROUPS 1
					BUFFER_POOL DEFAULT
					FLASH_CACHE DEFAULT
					CELL_FLASH_CACHE DEFAULT
					)
				)
ENABLE ROW MOVEMENT
/

SQL>  sho parameter undo

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
undo_management                      string      AUTO
undo_retention                       integer     3600
undo_tablespace                      string      UNDOTBS1