The TN3270 protocol supports both SCS (LU1) and 3270DS (LU3) printer sessions. When a client connects and requests a printer session, the type of printer is negotiated by the client and server. Most CICS applications that send output to a printer expect a specific type of printer (either SCS or 3270DS), so you must ensure your printer client connects as the correct type.
There are two main versions of TN3270: the original protocol, sometimes called "Classic TN3270", and "TN3270E" (for Enhanced). SCS printing is only supported with TN3270E. Most client software supports TN3270E but can often be configured to use Classic TN3270. If your client is using Classic TN3270, it will always be a 3270DS printer.
With TN3270E, a printer client session can request to be a 3270DS (also called LU3) printer or an SCS (also called LU1) printer, or both. Supporting both types of printing to a single client requires mainframe capabilities that Enterprise Server for .NET CICS does not currently support. If a printer client requests both types of printing, CICS will look for a TypeTerm resource definition for the requested terminal LU name. If the client doesn't request an LU name, or the requested device does not have an associated TypeTerm, or that TypeTerm's Device property does not specify "SCSPRINT" or "3790", then the printer type will be 3270DS.
To use SCS, a printer client session can either: