How to know can a program be enhanced?

Hi,

I am trying to enhance a program. I do Program -> Enhance and then Edit -> Enhancements Operations -> Show Implicit Enhancement options. I get context menu at the line and do ...Enhancement Operations -> Create. I enter the name of Enhancement Implementation and press enter, but then I get message Object XY cannot be enhanced; software component Unknown cannot be enhanced.

Can I change this setting? Where can I see is a program enhanceable or not (table, transaction...)?

Thanks!

KR,

Igor