It is important that your sample latency packets look just like SQL*Net packets. One of the best ways to do this is to use Oracle's tnsping command, found in the $ORACLE_HOME/bin directory.7 While both the ping and tnsping commands provide network latency times, the classic ping command is not good enough. Sharp network administrators managing a complex network infrastructure could possibly delay a standard ping packet, stop it altogether, or route it around the world a few times. So simply avoid this trap by issuing the tnsping command.

Take hundreds or thousands of tnsping samples. Don't sample once every second, or you might have an unsavory encounter on your way home from work. Create a simple shell script that runs tnsping once every 30 or 60 seconds, directing the output to a text file. And let this run for a couple of days. Do some fancy awk'ing and grep'ing, and then drop the data into an Excel spreadsheet to get a good understanding of the situation.

Besides calculating the typical mathematical statistics on the latency, such as the average and standard deviation, look for daily trends. It could be that during peak Oracle processing times, latency time skyrockets. Perhaps there is a lot of non-Oracle activity during this time, and the network is taking a beating, so the administrators are routing all other traffic (including your SQL*Net packets) around the problem! I have found that the network administrators may not know the Oracle system is experiencing network issues-that is, until you tell them about it. They are focused on support issues and ensuring the network is available (sounds like some DBAs I know).