Need help in DBMS_STATS - Oracle 10.1.0.5

Question

Folks, when I ran SCHEMA STATS using DBMS_STATS in my Oracle 10.1.0.5 db, I got error message. Pl help..
Lily,
===================================================
SQL> EXEC DBMS_STATS.CREATE_STAT_TABLE ('IDIS_DBA','IDISDBA_STATTAB','IDIS_REFERENCE_D');
PL/SQL procedure successfully completed.
SQL> rem -running table monitoring now
SQL> EXEC DBMS_STATS.ALTER_SCHEMA_TAB_MONITORING (ownname=>'IDIS_DBA',monitoring=>TRUE);
PL/SQL procedure successfully completed.
SQL> EXEC DBMS_STATS.GATHER_SCHEMA_STATS(ownname=>'IIS_DBA',options=>'GATHER AUTO');
BEGIN DBMS_STATS.GATHER_SCHEMA_STATS(ownname=>'IIS_DBA',options=>'GATHER AUTO'); END;
ERROR at line 1:
ORA-12801: error signaled in parallel query server P015
ORA-00904: : invalid identifier
ORA-06512: at "SYS.DBMS_STATS", line 12887
ORA-06512: at "SYS.DBMS_STATS", line 13181
ORA-06512: at "SYS.DBMS_STATS", line 13289
ORA-06512: at "SYS.DBMS_STATS", line 13249
ORA-06512: at line 1
Elapsed: 00:00:06.55
===========================BUT when I ran table level schema, It got thru....
SQL>
SQL>
SQL>
SQL> exec DBMS_STATS.GATHER_TABLE_STATS ('IDIS_DBA','BI_CLNT2',NULL, 20, FALSE, 'FOR ALL INDEXED COL
UMNS SIZE 75', NULL, 'DEFAULT', TRUE);
PL/SQL procedure successfully completed.
Elapsed: 00:00:00.10
SQL>

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