Oracle HTTP Server Performance Tuning Oracle Application Server Tips by Burleson Consulting

Since OHS is built on the proven capabilities of the Apache web server, there are not many things you can do to tune the actual server.  OHS must be tuned as part of the total application server. This is discussed in the High Availability and Performance chapter.  That said, there are a number of things you can do to improve OHS performance. 

Paging ? Anytime the operating system has to page memory to swap there is performance degradation.  Virtual memory allows an OS to over allocate physical memory, but it comes at a price.  Constant swapping of memory pages is a significant overhead.  The only way to stop excessive swapping is to reduce the memory footprint of the application or increase the memory on the server. 

Logging ? The more that must be written in logs the more time is spent writing to files.  One way to reduce the load on OHS is to reduce the Logging Level.  Once the system is functioning properly, you may be able to reduce the logging level.

Using .htaccess ? Directory Containers are used in the httpd.conf file so that all configuration is in one place.  A disadvantage is that each directory accessed requires that it?s access privliges be determine along with the access privileges of all directories above it.  If each directory contains a .htaccess file and all access privileges are stored there, then OHS only needs to read that one file.  The trade off is maintaining a .htaccess file in each subdirectory vs. the overhead of determining access privileges from Directory Containers in the httpd.conf file.  The more directories the system uses the more overhead of determining access privileges if .htaccess files are not used.

KeepAlive ? ALWAYS SET TO ON!!!  This parameter allows multiple requests to be serviced on a single connection.  This reduces the overhead of creating and dropping network connections. This can have a significant impact on OHS performance.

OHS Load ? The Enterprise Manager web console provides a large range of performance/load metrics.  Monitoring these metrics can help you determine the load your application places on OHS.  You must remember to monitor during appropriate times to insure that you are gathering appropriate statistics.  Web server usage fluctuates continuously, depending on work schedules, time of day, or the day of the week.  You must insure that you are gathering statistics to account for these variances.  

Also remember that some metrics reported are for the entire application server.  Throughput and response time will include actions performed by other parts of the application sever and possibly an interaction with a database.

Monitoring the Oracle HTTP Server with Enterprise Manager

Oracle provides a web-based interface to monitor all parts of the Application Server, including OHS.  To access this interface, insure that Enterprise Manager (EM) is running and if not, you will need to start it.

$ORACLE_HOME/bin/emctl status em
$ORACLE_HOME/bin/emctl start em

Open a web browser, connect to the application server (http://server_domain_name:port), log onto Enterprise Manager, and navigate to the instance page.  The OHS is designated HTTP_Server in the system components list.

Figure 1: Enterprise Manager Instance Page

If there is a need to start/stop/restart OHS, select the check box next to HTTP_Server, select the appropriate button, and EM will execute the command. When you make changes to the HTTP_Server, EM will write the change to the httpd.conf file and restart the OHS.  To get OHS details, select the HTTP_Server link to get the HTTP_Server page.

Figure 2: Enterprise Manager HTTP_Server Page

The data on this page is a snaphot of OHS performance at the time the page was loaded.  The data is not updated unless you refresh the page.  Many of the directives set in httpd.conf can be verified and changed from this and subsequent pages, to include creating Virtual Hosts and looking at logs.  Selecting Create in the Virtual Host section will walk you through a setup wizard (detailed at the end of this section). 

The Administration Section contains all the directives from httpd.conf.  Selecting Server Properties in the Administration section will take you to the directives in the first section of httpd.conf.

Figure 3: Enterprise Manager Server Properties Page

All changes made in EM are written back to the httpd.conf file and OHS is restarted to load the new parameters.  All of the directives in httpd.conf can be found in the Administration section of the HTTP_Server page. 

Now that we can use EM to maintain OHS, lets look at some of the metrics that we can use to monitor OHS?s performance. Start at the HTTP_Server page (Figure 2 above) and select the Status Metrics link.

Figure 4:  Enterprise Manager HTTP_Server Status Metrics Page

 

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