Databases Reference
In-Depth Information
Chapter 16
Tuning RMAN
For most backup and recovery scenarios, you'll find that RMAN's out-of-the-box performance is acceptable. RMAN is
a reliable and efficient tool for backing up, restoring, and recovering your database. However, sometimes (especially
with large databases) you will be required to tune and increase the performance of RMAN jobs. These are the most
common reasons you'll encounter for needing to tune RMAN:
•
Your backups are taking too long.
•
The performance of the overall system is unacceptable during backups.
•
Restore and recovery operations take too long.
Before you start the tuning process, you must first clearly identify what you want to accomplish and how to
measure success. If you can't measure performance, then it is difficult to manage it. Without specific criteria, you
won't know when you have successfully improved the job being tuned.
For example, your business may require that the production database not be down for more than six hours. As
part of your backup and recovery strategy, you have regularly been testing how long a complete restore and recovery
of your database will take. If you discover that the test environment restore times have been steadily increasing and
are now taking close to six hours, you should start the tuning process.
In the situation we've just described, you would have a specific requirement that the restore and recovery
operation must take less than six hours. You also have been testing and gathering metrics and can show a historical
trend toward unacceptable performance. Having specific goals and a way to measure performance are the first steps
toward being able to tune successfully (RMAN or otherwise).
Here are the general steps that we recommend when trying to improve backup and recovery performance:
1.
Identify measurable business performance requirements.
2.
Collect data and measure performance.
3.
Identify bottlenecks.
4.
Make adjustments that will alleviate the worst bottleneck.
5.
Repeat steps 1-4 until your performance goals are achieved.
You'll have to work with your business to figure out what the specific and measurable performance goals are for
your backup and recovery processes. This chapter will assist you with steps 2, 3, and 4 in the tuning process.
Before going any farther, we feel compelled to point out the obvious, which is that isolated tuning of single components
of your system will not necessarily lead to a holistic optimized result. Your backup and recovery performance will be
impacted by the architecture of your entire system. This includes components such as the following:
•
CPU
•
Memory
•
Operating system
