Very slow insert

Question

Oracle 9i, Linux Redhat Enterprise 3.0 (4CPU, 4GB of RAM)
Here is the situation: every 3 minutes we load a bunch of ASCII files into the database .
For each file we do the following: load it into temporary tables, do some processing and tranforming, and then insert everything into main tables.
These main tables are partitioned by date within composite index for 3 columns. Two largest of them get around 338 285 531 rows a month.
My problem is that from time to time, the last step, insert into main table takes too much time. Normally, it takes some 6 seconds to load the file and do the processing(using sqldr direct=y), and 85-90 to do the insert into main table. On some days, insert takes some 110 seconds (load and processing still take 6 seconds).
Tablespace that contains is locally managed.
What could be the reason for such drastic slow-down?
TIA,
Lux

Answer 1

Here is the way i load data
ASCII->load_new_table->main_table
From ASCII to load_new_table using SQLLDR direct=y, and from load_new_table to main_table using insert /*+ APPEND NOLOGGING */ ( direct path insert).
better to either upgrade it to ASSM tablespace or increase the freelist ,initran it might help ?>>>>I'm not for sure in this point. May u you give more detail? or tell me the way to do it.
And how to check whether the table being sized correctly??
TIA,
Lux