Nitin - this isn't my area of expertise but your question made me curious.
Looking at this technote: 1247688 (go to
www.ibm.com and paste that into the search box)
Client for Windows? V8.3 and 8.4
Most functionally comprehensive client for use with OnDemand
Best performance
Two-tier model; no mid-tier
...by implication I would say all clients other than the Client for Windows require the mid-tier; i.e., the CMOD z/OS mid-server to communicate with a CMOD z/OS server.
Ed