Portal support package level : highest of the SAP infrastructure ?

Hello,

We have a SAP EP 701 Portal Lanscape with SPS06 (Support Package Stack 06) and we intend to update the SPS level to SPS 7 or SPS8.

On the other hand we have a SAP ECC6 Ehp4 Landscape SPS05 and we also intend to update the support package level.

Our SAP EP and ECC6 system are both based on SAP NW 701, even though those systems are intalled on different hardware bowes, I was wondering whether they might some dependencies regarding the support package level ?

I vaguely remember that the Support package level of the Portal should always be highest of the whole SAP Infrastructure , but I couldn't find any sap documentation that might corroborate that statement...

Do you know if there are some dependecies between ECC6 ehp4 and EP 701 ?

Is it confirmed by SAP litterature ?

Thank you in advance for your attention

Best regards.

Raoul