I want to understand the Ehp technical background. I read throu almost all PDFs and notes. From them I assume the following:
An Ehp is similar to an SPS but in a bigger size.
An Ehp can contain new components in contrast with SPS which can contain only SPs for components which are already installed in the system.
So technically they are the same but the Ehp techology can install new components, and that's why SAP needed to introduce a new tool sapehpi to be able to do it in the background automatically.
So according to "Note 1064635 - SAP ERP Enhancement Packages: SP Stacks Release Info Note" , if you have an ERP 6.0 and want to update it but don't want to introduce new components you can apply SPS 15 which equals Ehp4 SPS3 state. But if you want to add new components you have two alternatives:
1. "Old fashined way": Install with SAINT and than patch with SPS
2. "New way": Install Ehp containing the new component and use sapephi (Ehp4).
But there is one more question unanswered for me: if this true what exactly and technically mean the version difference (for example: 600 -> 604 (Ehp4))?
I appriciate any comment.