Oracle9iAS Performance Tuning Oracle Application Server Tips by Burleson Consulting

This chapter deals with the most important areas of Oracle9iAS administration, optimization and high availability.  Even if you have done a superb job in installing and configuring Oracle9iAS, if the system is not always available or if the performance is poor, then you have not succeeded in your job.  This chapter will cover the following topics:

• Overview of Oracle9iAS performance

• Monitoring Oracle9iAS

• Oracle9iAS tuning with component parameters

• Tuning the Oracle HTTP Server (OHS)

• Tuning the Oracle9iAS Web Cache

• Load balancing of Oracle9iAS components

• Oracle9iAS server monitoring and load balancing

Overview of Oracle9iAS Performance Tuning

Being complex, an Oracle9iAS environment has a huge amount of tuning opportunities.  For example, the Oracle database back-end has more than 250 initialization parameters, each Oracle9iAS component has many interrelated parameter and configuration settings, and each server has dozens of tuning options.  Tuning any one of the Oracle9iAS components is challenging by itself, but when we consider the complex interactions between Oracle9iAS components, there can be an overwhelming amount of tuning activity.

We must start by noting that every Oracle9iAS system has a bottleneck.  Even a well-tuned Oracle9iAS system will have some resource that comprises the majority of the response time.  The best approach is to identify the component that is the bottleneck and then drill-down and identify the component resource that is responsible for the latency.  The bottleneck may be hardware related (CPU, RAM, Disk I/O, or Network shortages), or software related (locks, latches or contention).

There are two approaches to Oracle9iAS tuning, the reactive and proactive approach.  In the reactive approach, we receive a response time complaint from the end-user community and we use tools such as OEM to ascertain the cause of the performance problem.  In the proactive tuning approach we collect detailed statistics from all Oracle9iAS components, analyze the data, and develop predictive models that can predict those conditions that will impede performance.

Let?s start by examining the tuning ?knobs?.  By altering a knob, we adjust the configuration and resources for the Oracle9iAS farm and change the processing characteristics.  Common knobs or Oracle9iAS include three areas, physical server (hardware-level) tuning, parameter tuning and RAM cache tuning:

Server tuning

• Hardware configuration ? Adding RAM of CPU resources to existing servers will improve the throughput on the server

• Hardware load balancing ? The addition of new servers to the Oracle9iAS farm and relocating Oracle9iAS components onto the servers allows for scalability during times of peak usage.  Spare servers can be configured with both Web Cache and Application Server, and the appropriate components can be started as-needed.

• Server parameter tuning ? Adjusting the parameters on your server can have a huge impact on the performance of the Oracle9iAS components running on that server.

Parameter tuning

• Oracle9iAS parameters - Adjusting the Oracle9iAS configuration parameters for each Oracle9iAS component has influence on performance and throughput.

• Database parameters ? Because most Oracle9iAS systems are disk I/O intensive, adjusting the Oracle database parameters for the Infrastructure database (iasdb) and the back-end database can heavily influence performance.

RAM cache tuning

• Data buffer tuning ? Adding RAM to the database db_cache_size on the Oracle Infrastructure and back-end database can greatly reduce disk I/O and improve throughput.

• Web cache tuning (Oracle9iAS Web Cache) ? Adding RAM to the Oracle9iAS Web Cache can improve the delivery rates of HTML and XML though the Oracle HTTP Server (OHS).

As we mentioned, proactive tuning is the best approach for the tuning of Oracle9iAS because we can analyze historical database information and observe trends and identify performance thresholds.  In order to do proactive monitoring we must develop data collection mechanisms for the servers and each Oracle9iAS component.  Let?s take a look at Oracle9iAS monitoring.

Monitoring Oracle9iAS

In order to develop a coherent picture of overall Oracle9iAS performance we must collect data from a variety of sources. Things to monitor and adjust:

• Resource usage monitoring ? Assuming that each Oracle9iAS component is optimally tuned, any hardware-related overload must be addressed with more hardware.  The solutions may be to add a new application server, add RAM or CPU to existing servers, or install faster disks.  In UNIX or Linux you can monitor Oracle9iAS servers with the vmstat utility, top, glance or iostat, and store the data into Oracle tables for time-based resource analysis.  In a Windows environment you can use the Windows performance monitor to measure hardware usage.  We will explore Oracle9iAS hardware monitoring & tuning later in this chapter.

• Response time monitoring ? Several components within Oracle9iAS allow you to track overall response time and the components of response time.  For example, web applications using the Oracle9iAS Forms Server can use the Forms Server log to generate detailed response time report.  We will address this in greater detail later in this chapter.

• Wait event monitoring ? Perform a wait even analysis on each component of Oracle9iAS can provide insights into the main source of latency for each Oracle9iAS component.  For example, in the Oracle database, a STATSPACK report will show the top-5 database wait events (Listing 10.1):

Top 5 Timed Events
~~~~~~~~~~~~~~~~~~                                % Total
Event                           Waits  Time (s)  Ela Time
------------------------------  -----  --------  --------
CPU time                                     30     91.43
direct path read                   95         1      3.53
control file sequential read       54         1      2.33
log file parallel write            62         0       .95
db file parallel write             20         0       .68

Listing 10.1: STATSPACK report of top-5 wait events

This is an excerpt from "Oracle 10g Application Server Administration Handbook" by Don Burleson and John Garmany.