I want to know, can we connect OPC Client to OPC UA by DCOM setting?
OPC UA security is based on certificates than DCOM. Classic OPC was built on MS operating systems which used DCOM but OPC UA is independent of OS.
OPC UA does not use DCOM. You can read some more about it here: Unified Architecture - OPC Foundation
What are you trying to achieve exactly? Get data in/out of PI?
Retrieving data ...