Differences between BTAM and VTAM application programs
Table 1 shows the major similarities and differences between VTAM® application programs and BTAM application programs. The chart provides assistance in evaluating the effort needed to revise the application program for communication with VTAM LUs.
BTAM can request sessions only with dedicated devices. Hence the next section about converting from a single-domain to a multiple-domain network offers hints that apply equally to BTAM application programs that are being converted to VTAM.
| Functions provided | VTAM application program | BTAM application program |
|---|---|---|
| Define line groups | Can be defined during VTAM definition or dynamically after VTAM is started | Use DCB or DTFBT macroinstruction to define line groups |
| Define terminals | Can be defined during VTAM definition or dynamically after VTAM is started | Use DFTRMLST macroinstruction |
| Initialize program | Use OPEN macroinstruction | Use OPEN macroinstruction |
| Sessions with terminals established dynamically | Use OPNDST macroinstruction | Not available, because terminals are statically connected when application program's job step is initiated |
| Release control of a terminal to another program that requests a session with it | When requested, use CLSDST with OPTCD=RELEASE specified | No comparable function |
| Receive input | Use RECEIVE macroinstruction | Use READ macroinstruction |
| Receive input from any terminal | Specify input can be from any terminal | Must poll each line separately |
| Receive input from a specific terminal | Specify input is to be received from a specific terminal | Specify terminal list entry |
| Send output | Use SEND macroinstruction | Use WRITE macroinstruction |
| Have data schedule for output from access method buffers (output buffering) | Specify that the data is scheduled for output | No comparable function |
| Test, display, or modify control block fields | Use manipulative macroinstructions: TESTCB, SHOWCB, MODCB, or use assembler language instructions | Use assembler language instructions |
| Record transmission errors | Performed by NCP and VTAM | Use error recording macroinstructions |