Report Slow Down

Question

We have a report that used to produce a 1000+ page pdf in
about 2 minutes. It has gone to producing a 200+ page report in
about the same amount of time. No change to the data, database,
report or environment, it just suddenly slowed down and nothing
seems to be able to make it go back to decent performance on large
record sets.
Server reboots don't help, any ideas or thoughts would be
appreciated.

Answer 1

Hello
I followed some Donald's suggestion and went through some explanations he's given on its web site to try to figure out how could I speed up the database 10g since we migrated from 8i to 10g.
Here are default values in our 10g influencing the COST BASE OPTIMIZER
OPTIMIZER_FEATURES_ENABLE=10.2.0.1
OPTIMIZER_MODE=ALL_ROWS
OPTIMIZER_INDEX_COST_ADJ=100
I launched his script below provided to see time waited between full scan table
('db file scattered read representing by the c3 row and the
sequential read representing by the c4 row)
select
sum(a.time_waited_micro)/sum(a.total_waits)/1000000 c1,
sum(b.time_waited_micro)/sum(b.total_waits)/1000000 c2,
sum(a.total_waits) /
sum(a.total_waits + b.total_waits)
) * 100 c3,
sum(b.total_waits) /
sum(a.total_waits + b.total_waits)
) * 100 c4,
sum(b.time_waited_micro)/sum(b.total_waits))/
(sum(a.time_waited_micro)/sum(a.total_waits)
) * 100 c5
from
dba_hist_system_event a,
dba_hist_system_event b
where
a.snap_id = b.snap_id
and
a.event_name = 'db file scattered read'
and
b.event_name = 'db file sequential read';
there is the output of the script
C1 C2 C3 C4 C5
.002438964 .002888595 24.6526611 75.3473389 118.435332
So the time waited for full scan(c3) table is most faster than index sequential read(c4:index probe)
I changed the parameter OPTIMIZER_INDEX_COST_ADJ and OPTIMIZER_MODE
alter system set OPTIMIZER_INDEX_COST_ADJ=20 scope=both;
alter system set OPTIMIZER_MODE=FIRST_ROWS_1000 scope=both;
I lauched aigain the script above, but the output shows the result below
C1 C2 C3 C4 C5
.002438964 .002888595 24.6526611 75.3473389 118.435332
this output isn't different than the first one, so does this mean that INDEXES are not well designed or WHAT ELSE?.
Wich parameter could I enable or change to decrease the C4(index sequential read wait time?
Thank you for your help