OMEGAMON installs as a set of started tasks on z/OS. Which started tasks get installed depends, of course, upon which OMEGAMONs from the suite you are running, and what features of OMEGAMON you may have configured. For example, if you are running OMEGAMON XE for DB2 or OMEGAMON XE for CICS, the agent task for the XE GUI interface (aka the TEMA), is something that you may or may not run, depending upon whether or not you use the Tivoli Portal GUI interface. The TEMA is not required if all you are doing is classic 3270 interface.
When you are looking at optimizing OMEGAMON, the first thing to understand is the CPU usage of each of the OMEGAMON address spaces. I suggest doing something like looking at SMF30 record output (or an equivalent), for each of the OMEGAMON started tasks, and generate a report that will let you see a summary of CPU usage by task. Look at the data for a selected 24 hour period, and look for patterns in the data. For example, first look for which tasks use the highest CPU of the various OMEGAMON tasks. Different installations may have different tasks that use more CPU, when compared to the other tasks. It really will depend upon what OMEGAMONs you have installed, and what you have configured. Once you have identified which OMEGAMON started tasks are using the most cycles relative to the other OMEGAMON tasks, that will provide a starting point for where to begin your analysis.