Moving data between two schemas

Question

I need to move data between to schemas. I have a created packaged code to accomplish this. The problem is the execution time. When running the insert statements from the source schema to insert data into the target schema, it takes considerably longer to complete the statement than if I copied the tables from the source schema into the target schema and executed the same statement in the target schema. Any insight as to why this might be?
Also all data resides on the same physical disk, running version 10g on a W2K server.
Thanks in advance
Here is a sample of one of the insert statements:
INSERT INTO target_table(tt_id, tt_disp, tt_date, tt_emp_1, tt_emp_2, tt_emp_3)
SELECT src_tab.src_id,
src_tab.scr_disp,
src_tab.scr_date,
src_tab.scr_emp_1,
src_tab.scr_emp_2,
src_tab.scr_emp_3
FROM
(SELECT
row_number() over(
ORDER BY SUBSTR(fn_cil_sort_format(SUBSTR(src_cil,
1, 8)), 1, 4), SUBSTR(src_cil, 4, 8)) AS src_id,
scr_disp,
fn_date_format(date_time) AS scr_date,
v_convert AS scr_emp_1,
v_convert AS scr_emp_2,
v_convert AS scr_emp_3
FROM source_table
ORDER BY SUBSTR(fn_sort_format(SUBSTR(src_cil, 1, 8)), 1, 4),
SUBSTR(src_cil, 4, 8)) src_tab
WHERE scr_disp IS NOT NULL;

Answer 1

In addition to the above post, you should create the table initially with NOLOGGING. create table as select has the ability to bypass logging. This should increase performance very much. No log writes will have to be taking place.
Lee