Databases Reference
In-Depth Information
Here are some causes of and associated solutions for disk bottlenecks:
•
Stretching memory to its limit
—When memory is low, paging to disk
occurs more frequently. Resolve the memory issue.
•
Poorly optimized application code
—Develop or tune your application to
avoid unnecessary disk reads or writes. See “The Database Application,”
page 269.
To detect a disk bottleneck, gather information about your system to answer
the following questions:
•
Is excessive paging occurring?
A memory bottleneck can resemble a disk
bottleneck, so it's important to rule out a memory problem before you make
disk improvements. See “Memory,” page 107.
•
How often is the disk busy?
If your disk has a sustained rate of disk activity
of 85% or more for a sustained period and a persistent disk queue, you may
have a disk bottleneck.
CPU
The primary symptom of a CPU bottleneck is that the application is slow when
multiple users are using it. A CPU bottleneck negatively affects scalability. For
detailed information about CPU, see “CPU (Processor),” page 112.
Here are some causes of and associated solutions for CPU bottlenecks:
•
Insufficient CPU capacity
—Install additional processors or upgrade to a
more powerful processor.
•
Poorly optimized application code
—Develop or tune your application to
minimize CPU use. See “The Database Application,” page 269.
•
Poorly configured database drivers
—Understand the runtime perfor-
mance tuning options for the database driver you are using, and configure
the driver to use the appropriate options to minimize CPU use. See “The
Database Driver,” page 270.
To detect a CPU bottleneck, gather information about your system to answer
the following questions:
•
How much time does the CPU spend executing work?
If the processor is
busy 80% or higher for sustained periods, the CPU can be a source of trou-
ble. If you detect high CPU use, drill down to individual processes to deter-
