reading var. via BPC framework/TREX (TREX_EXECUTE) in Planning Function

Hello.

I'm the beginner in BW area.

I need to read variables (in my case Data Version and Production Center - multiple values in Production Center) in Planning Function.

I'm using BPC framework (Interface IF_RSPLFA_SRVTYPE_TREX_EXEC).

In method TREX_EXECUTE is access to class CL_RSPLFS_PARAM_SET.

the methods from this class returning Data version, Production Center also, but only one value, e.g. if You provide on filter two production centers for US and FRANCE, only the first one will be provided.

I tried to use CL_RSPLFR_CONTROLLER=>GET_ACTIVE_CHARSEL - data version was returning, but Production Center not - only HANA view(?).

as I said for the beginner it is quite strange.

Thanks.

Regards,

Tomasz