The technical and logon parameters are used by the sender RFC adapter to get the metadata from the SAP back-end system by using the interface of the function module. These parameters can be found under the RFC Metadata Repository (MDRS) parameters.
The MDRS is accessed only once because the metadata is temporarily stored in the adapter cache and it can be reused for subsequent calls of the same function module.
Additional note about the RFC library librfc32(.dll)
The classic RFC library librfc32(.dll) will no longer be supported after March, 31, 2016. It is replaced by the new SAP NetWeaver RFC Library. Check Notes: 1025361 and 1005832. A limitation of this new RFC Library is, that it does not support communication between two external systems. For example, it is no longer possible to connect an external program with SAP Process Integration (PI) by using the PI RFC Adapter. The usage of pure RFC should be avoided by using proxies instead.