Tuning issue, 10046 trace and Scheduled Jobs

I have a pl/sql batch process running on 10g (using scheduled programs/schedules/jobs) on windows that runs nightly starting at 3 am and part of it calls 2 similar procedures; 3 inserts into global temporary tables, followed by a call to dbms_stats to set the number of records, followed by an insert as select full outer joining the 3 GTT's (~155k narrow records each) with a bit of logic into a permanent table.

These insert statements when run at night as part of the batch take 35+ minutes, when they are run at any other time they take less than 10 seconds (210 times slower) whether by calling the package or just running the insert statements.

I have looked into everything I can think of. I have checked the explain plans on the 2 queries and they are optimal, statistics and indexes are fine.

Yesterday I added 10046 tracing around the 2 procedure calls to see what was taking so long within those queries however no trace file was created. When I just ran the package, it ran quickly and the trace file was generated.

1. Has anyone ever seen a 10046 not generate a trace file when called by a scheduled job?
2. Any ideas on why these "insert as selects" from the 3 GTT's would perform differently when run as a schedule job?

Thanks,
Ken

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