optimize performance during oracle11i upgrade

[Dave Chamberlin]

Hello,
We are working on out upgrade from oracle applications 10.7 to 11i and our database is about 75GB. I have done several test upgrades and have the patching down to 25 hours or so (using rp8400 w/10 CPU and VA7410 disk array). I am looking to see if I can improve the patch time by changing init parameters for the database (block buffers, etc), resizing log files, or adding more spindles to the rp7410. The box has 20GB of RAM. The db_cache_size is 1200M, shared pool is 500M, the java_pool is 60M. I attached a copy of the initORA file. Any suggestions from appreciated.

[Steven E. Protter]

Shalom Dave,

I do not think your patch performance will be significantly improved by changing block size on init.ora or the OS.

A properly tuned box in general will assist in faster execution of this work.

I recommend dbc_max_pct be low and nearly the same as dbc_min_pct to prevent double buffering of oracle data.

Tweaking init.ora may help but I have suggestions other than the negative above.

SEP

[Patti Johnson]

Dave,

Review the upgrade log and find those steps that take the longest - then look for performance patches from Oracle - or tuning steps that you can take yourself.
Also set the number of workers as high as possible - with 10 cpu's you should be able to support 20 workers without a problem.
You can also take the db out of archivelog mode - just make sure you backup before and after the upgrade.

I've done a couple of these upgrades and depending on the products that you have installed (HR, Payroll, AR were problem children for me) you may find significant performance patches, but you need to look at the individual scripts being run by the upgrade to find the ones that need attention.

Patti

[TwoProc · Accepted solution]

Dave, the only thing that springs to mind that could improve things is your db_cache_size (block_buffers) - on a test box - try increasing that to 10G (just for the upgrade). Also, your shared pool is too small for 11i anyways, so go ahead and set it at 1G for the upgrade (and try to leave it at least there afterwards).

This may have anything from a profound impact on your upgrade, to very little impact on the process.

Also, I agree with the previous post about the number of workers, on a 10 way server I'd run with 25 workers (2.5x num cpus), but there is no hard and fast rule on that.

On another note -
Before your upgrade, you should be running some tests for comparison on performance from old to new. I think you need a much bigger buffer_cache for running Apps 11i, and I believe you need quite a bit more in the shared pool (I use 2G). Your java pool might be just a little light, I'd add 15M to it, making it 75M. Use statspack and some testing to see how you are doing for running some processes in the old system versus the new.

Except for running out of room in the box for operational processing, DON'T be afraid of adding more buffer cache, unless your buffer cache hit ratio at the worst period of the day stays steady at 99%, and doesn't drop off (by much if any). You'll hear that it's expensive to run large buffer caches in Oracle, and that you can slow the system down by doing so. I'm guessing that when servers used to run at 25,50, and 75Mhz - it may have been true, but it's certainly not the case any more. Just make sure you KNOW what your ram consumption is AFTER the database is already up and running and users are on it and leave that as headroom (and then some), so that you don't go into swap during the day.


Also, on some of your processes (heck, maybe even lots of them) you'll be missing some indexes that make the queries and data the way you use them run correctly. Some quick reviews of long running code for processes that show the largest slow downs after the upgrade would be good to do before go live. Many of them (but not all) will be solved by creating custom indexes to facilitate processing your seeded reports and activities. This is because the seeded indexes can't fully address how your company chooses to use and report with the tables and system provided by the application.

Good luck!

[Volker Borowski]

Hi Dave,

I'd give a try to configure new UNDO Management and automatic PGA beforehand.
Automatic PGA should give you better memory handling for the SORT-Buffers.

Monitor the Controlfile_write_activity during the upgrade. If you consider to disable archive logging, consider to use a single Controlfile during the upgrade (takes off two sync writes on Commit during upgrade), but DO NOT FORGET to reestablish the mirrorcopies afterwards.

Increase Online Redolog size to avoid checkpoints, you will get one Checkpoint for every Logswitch.
How big are they ?
Check the alertfile for how many checkpoints you encounter in this upgrade.
Check the alertfile for "... not complete"

In case you have plenty of CPUs, increase the number of DB_WR processes.

java_pool seems small, shared pool as well, and you should surely increase db_cache_size.

db_block_checksum is quite expensive I mind to remember. May be you can switch it off for the upgrade ?

Good luck
Volker

[Dave Chamberlin]

Thanks for the replies. I will definitely increase the buffer cache - I have lots of RAM. I reviewed the oracle logfile and there are a couple hundred of the "checkpoint not complete" messages during the main upgrade. The redo logs are 100M. Would you suggest increasing the size of those - if so how much? How expensive are checkpoints? thanks

[TwoProc]

Well, it depends on how often you're switching. But, since you're not always completing them before the next one comes up, it would be really safe to double it, as 200M isn't very large at all, and then see how you're doing.

Also, check that your redo's cache size is large enough.

[Dave Chamberlin]

Do you mean log buffer? If so it is currently 4M. if not - what parameter do you mean? What would you consider optimal?

[Eric Antunes]

Hi Dave,

Redolog sizes are dependent on the activity of each database but you can monitor the redolog switches to check if yours are undersized.

My redo related parameters are:

log_checkpoint_interval = 40960
log_buffer = 1048576
log_checkpoints_to_alert = true
3 groups of 10Mb

Also, during the upgrade, disable timed_statistics...

Best Regards,

Eric Antunes

[Eric Antunes]

After setting log_checkpoints_to_alert to true and restarting the database, you can monitor the log switches with:

$tail -fn15 /.../alert_.log

Best Regards,

Eric Antunes