Application Monitoring
Application monitoring is looking at how the interaction between
an application, such as SAP or Oracle Financials, is being maintained. The
connection between an application and the underlying database is often a rather
complicated affair. Typically these connections are maintained through what is
referred to as a multi-tier system utilizing a product referred to as an
application server. The application server lies inbetween the path of the user's
computer and the database. Within that server is the code that translates the
request that the user had
into the information that needs to be sent to the database. Once the application
server receives all the information it returns it to the user in a nicely
formatted presentation that they on the screen.
Within these application servers (which is basically just a fancy way of saying that it is a computer that is devoted to handling applications) are usually a variety of programs. One of them will be the web server that takes the initial request from the user. Today's programs are based on Internet technology which means that the only program that needs to be on your computer desktop is an Internet Browser like Netscape or Internet Explorer. It is very much like going to a website, except that in this case it is a website within your company and the information being looked at is about your customers. So we have the webserver, there are a few other smaller webserver like programs usually present (tomcat servers) and very often a security authentication program and possibly a caching program to store already processed results in case we can use them again, the actual application server program that runs the program that 'the office' uses and then a few other miscellaneous programs that keep everything tied together.
In a bigger operation a lot of these programs will in themselves be put on their own server so they don't run into conflicts running on the same computer. Now, if we had the user at their desktop, a webserver on one computer tied in to the application server on another server and the database on the final computer, this would be referred to as a 4-tier program, representing the four different computers that are being used to get everything running together.
So what needs to be monitored?
In a multi-tiered environment such as this there are several things that need to be monitored. The connection speed between the various computers is of course of interest to us, as is the time that it is taking to process the requests from the application server to the database. We are also interested in how many times we are able to reuse a given request, since if we have the results already, it would be much nicer if we were just able to cache the results and when the same query came in again, just give them back our results from the cache. Another area to be monitored is the contention for resources that may occur on any of the servers as a result of unusually heavy request times. Then there are the normal problems that arise in the computer world such as loss of connectivity (one computer cannot talk to another for whatever reason), running out of disk space (often caused by an accumulation of log activity data).
The nice aspect of this is that nowadays we have been able to automate so much of what we do that when problems like this occur, we can actually have this information sent out to a cellular phone that a DBA would carry or to a pager for whoever was on call, and this will automatically notify them of the problem. Even if they were not physically at the office, they would be able to dial in from where ever they were with their laptop with the only condition being that they have to be near a phone jack. And today, it can actually be done using something as small as a Palm Pilot and a cellular phone with a connector that joins the phone to the Palm Pilot.
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