RE: Database performance during hot backup
Date: Fri, 30 Mar 2012 13:03:05 -0400
A little bit more information on the way we are conducting these tests. We are in the process of implementing hot backup in our Oracle FMW SOA suite environment and we are trying to assess if our users could potentially experience any slowdown during the backup process so that we can set their expectations accordingly. The FMW BPEL console provides a facility where you could simulate the load that you would run in real-life (think time, iterations, etc.) on various services. The majority of the BPEL statements are INSERT based because they insert data into the database. We are running tests with two scenarios: (a) DB not in hot backup mode (b) DB in hot backup mode. During our test, we are NOT actually snapping the backup (we are using EMC NAS for this RAC database and use the snap technology for backup) at the storage level.
The BPEL console is reporting that when the DB was not in hot backup mode, the transaction timings were much better than when it was in hot backup mode. I have not actually run AWR during the test to see whether it is the LGWR that is causing the issue or something else. I just wanted to find out first, at a high level, whether to expect any performance degradation during hot backups or not.
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Jonathan Lewis Sent: Friday, March 30, 2012 12:22 PM
Subject: Re: Database performance during hot backup
If you're doing a backup you're presumably copying the database files -
which may mean that every db file read is a little slower, which may be
enough to slow down the DML - especially since DML often requires
to be maintained and index maintenance often leads to random single block
reads. The I/O due to backing up could also slow down the log file parallel
writes, increasing the time for log file sync waits.
Given that you could be increasing the size and number of writes to the
file you've got another reason for seeing slower DML times, even if the log
writes isn't under any particularly heavy load.
- Original Message ----- From: "Hameed, Amir" <Amir.Hameed_at_xerox.com> To: <oracle-l_at_freelists.org> Sent: Friday, March 30, 2012 2:37 PM Subject: Database performance during hot backup
I am trying to understand if it is expected to see performance degradation of DML transactions that are active during a hot backup. It is my understanding that the only noticeable thing that happens during a hot backup for DML statement is an increase in the amount of redo generation and that is because Oracle starts to log full images of data blocks before a change is made to a data block. I am not aware of any impact on performance while in hot backup mode, unless the LGWR is being constrained for some reason.
http://www.freelists.org/webpage/oracle-l Received on Fri Mar 30 2012 - 12:03:05 CDT