What does it mean for an application to be 'underutilized or not utilized'? The second case shows up surprisingly often and is fairly easy to identify. Underutilization can show up due to having more copies of a licensed application than you need, running different applications that provide overlapping business functionality, or just applications that are poor matches for your actual business requirements.
I have talked some in the past about the importance of understanding your portfolio of applications. A large part of this understanding depends on using the subject matter expertize, tools, logs, and other resources available to you to build accurate inventories, determine inter-application and business process dependencies, and track temporal properties.
Obviously, if you don't have an inventory, you have no hope of identifying underutilized apps. A surprising result of a meticulous inventory is that you often discover significantly more applications than you thought you had. And more copies of applications than you were aware of. Multiple copies present an opportunity for consolidation and reduced license costs and is a potential case of under-utilization of each instance. Merging instances normally leads to improved utilization.
The existence of an inventory enables mapping to a business model - at which point you can identify functional duplication and another opportunity for improved utilization. Duplicates may be different COTS products, multiple custom applications, or a combination of both. In any case, consolidating functionality will ultimately lead to lower costs and simpler operation. Consolidation isn't free - often you will need to deal with the issues of data retention, merging of archives and replacement of interfaces. But normally this is a major win.
HP's experience transforming its own IT infrastructure is a poster child for this kind of activity. The statistic I never tire of repeating is the consolidation of more than 6,000 applications down to 1,500.
The dependency relations permit transitive usage analysis. I'm sure many of you have seen the following more than once - a report is produced, sent to someone, they pull out some small portion of the report and type it into another system. Of course the worst cases are those reports that are no longer needed but still continue to be generated. The first case is an opportunity for more efficient processing, the second another chance to delete an application.
The temporal properties of applications can sometime be hard to track, depending on your infrastructure. But it can be extremely satisfying to look at some distillation of your logs and identify applications that have not been run in five years and can be easily eliminated.
Of course HP stands ready to provide assistance in your efforts to dramatically improve the utilization of your application portfolio based on our extensive experience in Application Rationalization.