Hi Apostolos,
In the NCP configuration (Gen) for the FEP look for the keyword "LLCLIST=", and QLLC is "LLCLIST=LLC3". If there are other LLCs also coded on the LLCLIST, that means that those LLCs could be dynamically selected when the connection is established, so it becomes ambiguous. In newer FEPs, with "900" frames and running V7R4 NCP, QLLC can be offloaded to the 900 by the use of ODLC. Look for the "X25.MCH" statement and "ODLC=YES". If all of the X.25 resource definitions are under these ODLC lines, then it can only be QLLC.
Rgds, Dan