Parallel Query Error (Ora 12801 Ora-00904)

Question

when i run this particular query in a report or in SQL it wrks
but some times it give the error .........
any one who could help ........ASAP
SELECT
D.DISTRIBUTOR_CODE "DIST_CODE",
D.DISTRIBUTOR_NAME "DIST_NAME",
O.OPERATOR_CODE "OPER_CODE",
O.OPERATOR_NAME "OPER_NAME",
O.ACTIVE_STATUS "Act",
r.receipt_no "receipt_no",
r.ch_or_dd_no "cheque",
r.receipt_date "receipt_date",
'' "channel Code",
'' "channel_name",
b. SUBS_IRD "ird_subs",
b.amount "amount"
FROM
dms_channel_dump z,
DMS_OPERATOR_MASTER O,
DMS_DISTRIBUTOR_MAIN D,
dms_receipt_header r,
DMS_BIFURCATION b
WHERE
b.channel_code = z.channel_code
and r.OPERATOR_CODE = O.OPERATOR_CODE
AND r.DISTRIBUTOR_CODE = D.DISTRIBUTOR_CODE
AND r.receipt_no = b.receiopt_no
union all
SELECT
D.DISTRIBUTOR_CODE "DIST_CODE",
D.DISTRIBUTOR_NAME "DIST_NAME",
'' "OPER_CODE",
'' "OPER_NAME",
'N' "Act",
r.receipt_no "receipt_no",
r.ch_or_dd_no "cheque",
r.receipt_date "receipt_date",
b.channel_code "channel Code",
z.channel_name "channel_name",
b. SUBS_IRD "ird_subs",
b.amount "amount"
FROM
dms_channel_dump z,
DMS_OPERATOR_MASTER O,
DMS_DISTRIBUTOR_MAIN D,
dms_receipt_header r,
DMS_BIFURCATION b
WHERE
b.channel_code = z.channel_code
and r.OPERATOR_CODE is null
AND r.DISTRIBUTOR_CODE = D.DISTRIBUTOR_CODE
AND r.receipt_no = b.receiopt_no
order by 4,7
ERROR:
ORA-12801: error signaled in parallel query server P004
ORA-00904: invalid column name
no rows selecte
REGARDS AND TIA
ADOLPH

Answer 1

If the data never changes, there would be no reason to gather statistics.
If the data changes, there may or may not be a reason to gather statistics. There is some risk to gathering statistics because that can cause query plans to change and you could find that a query that was working fine yesterday is running very slowly today. Failing to gather statistics, though, can have the same effect-- if a histogram on a column indicates that the maximum value of a date field is December 1, 2006 because you haven't updated statistics in a few days, the CBO may conclude that a query this column with a value of December 4 would return very few row, rather than the many rows that are really there, causing Oracle to use a different query plan. Oracle tends to believe that the latter risk is more of a concern than the former and in 10g regularly and automatically gathers statistics unless you susped that job. Some DBAs disagree with Oracle and prefer less frequent, more controlled statistics gathering.
If you GATHER AUTO, assuming your tables are set to MONITORING, Oracle gathers statistics on every table that has had more than some cutoff percentage of rows changed since statistics were last gathered. This cutoff is generally pretty reasonable, though ideally you'd probably want to gather statistics more frequently on smaller tables (adding 30 new rows to a 100 row table is probably more significant from a query plan perspective than adding 3 million rows to a 10 million row table) and less frequently on larger tables, more frequently on tables that have volatile data distributions (i.e. our DATE table) and less frequently on tables whose data distribution is relatively constant.
Justin