Lol... Guessing? I don't know if lower level details like exchange waits
show up in explain plans, ash or awr (maybe awr and trace). I saw the
exchange waits in OEM as I drilled into the session parallelism page.
The guessing comes from trying to prioritizing methods of approach and an
close approaching August release date. For August, I'm taking this 12
hours insert from old to hist table out of the foreground timed release and
put it in the background clean-up task (un-timed). That way I can release
the main tables back to live operational status quicker.
I will setup some tests in the performance lab for these approaches and see
how they benchmark. I'd like to find the best solution because I'm not sure
yet if this DB will never be purging data and inefficient and un-scalable
solutions will only get worse as the DB grows.
I do greatly appreciate all the great thoughts and creative approaches
given.
Thanks!
On Fri, Jul 27, 2018 at 2:44 PM Mladen Gogala <gogala.mladen@xxxxxxxxx>
wrote:
Why? Guessing is fun. It's like fantasy football, only with other people's
databases.
On 07/27/2018 01:19 PM, Insights wrote:
Stop guessing and get the awr, ash, and sql explain plan at the very
least.
Sent from my iPhone
On Jul 26, 2018, at 7:58 PM, Woody McKay <woody.mckay@xxxxxxxxx> wrote:
Ya got me thinking about the "load data by partition" idea...
I wonder if instead of insert dop 16 from select dop 16, what if I have
say 50 nonpartitioned tables (one for every partition) and dop4 insert into
the from *_old partition () all at the same time. Then do a partition
exchange from the 50 nonpartitioned tables to the main fully partitioned
table? The exchange is quick since it is just a data dictionary change.
This may be faster because the amount of DOP is higher. Maybe less
exchange waits? I'm assuming that the DOP 16 can't work on all 50
partitions all together as efficiently as loading all 50 nonpartitioned
tables?
Got me thinking...
On Mon, Jul 23, 2018 at 8:15 PM Karthikeyan Panchanathan <
keyantech@xxxxxxxxx> wrote:
What is the partition type involved here?
One option you can load data by partition into intermediary table(with
new columns) and exchange. This way you can run parallel sessions for each
partition and before exchange new table you can build at partition level.
You mentioned other db, have you thought about moving data from other db
to prod using data-pump?
Karth
Sent from my IPhone
On Jul 23, 2018, at 7:52 PM, Woody McKay <woody.mckay@xxxxxxxxx> wrote:
Hi gurus, I'm fishing for creative thoughts here...
12.1.0.2 RAC on Exadata with forced logging for standby
There's a refactoring process: (subpartitioned tables with millions to a
few billions of rows)
1. rename the main table to main_old
2. create the new_main table (no indexes or constraints at this point)
3. set table prefs for concurrent incremental stats
4. enable parallel dml
5. insert into new_main from main_old using APPEND PARALLEL 16 (note:
most tables are compressed)
6. create a PK or an index (as needed) on new_main
7. gather table stats on new_main
The insert in Step 5 took 9.5 hours... Total refactor process time was
about 13 hours.
Is there anything you can think of to make this process any faster?
I assume the APPEND hint isn't doing much because the DB has FORCE
LOGGING. Guessing alter table nologging wouldn't do much either. Can't
exchange from old to new since new mostly likely had columns added.
I've mentioned using alter table if we are only adding a few columns, but
the production DBA's are worried about chained-rows, fragmentation,
possible explain plan changes, etc. I'm not sure if they are justified in
their thoughts.
I've thought of doing the refactor in a diff DB (where I can truly have
nologging) and use transportable tablespace, but don't think that would be
any better.
Any Thoughts or ideas to try?
Thanks, as always - Woody
--
Sincerely,
WoodyMcKay
--
Mladen Gogala
Database Consultant
Tel: (347) 321-1217
