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.

Table 1. Major similarities and differences between VTAM and BTAM application programs
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