3270-Session Screen-Size Control

Although you can specify the screen size of the 3270 session in the PC/3270 configuration, the final screen size is determined by the host according to the SNA BIND negotiation.

Sometimes, you might want to use a particular screen size when it is difficult to have the host VTAM® table changed. The following method will satisfy your requirement; however, because it violates SNA rules, some applications that refer to the VTAM table only might not work.

Modify your workstation profile (.WS) to insert the following line into the [LU] section:

[LU]
InfScreenSize=Y

Personal Communications processes byte 24 of the host BIND image correctly and according to the SNA architecture. Byte 24 is the last 2 bytes of PSERVIC=X'028000000000000000000300' (03 in this case) in the log mode.

If byte 24 is X'03', the default screen size is 24 x 80 and the alternate is what you configured with PC/3270.

If byte 24 is X'00' or X'02', the default and alternate screen sizes are 24 x 80.

If byte 24 is X'7E' or X'7F', bytes 20–23 in the BIND control the default and alternate screen sizes.

If you have X'03' in the BIND image, you can customize whatever screen size you want. The host will query Personal Communications and use the alternate screen size.

The following table shows the details of the BIND image processing:

Byte in BIND by Host					Result (screen size)
24	20	21	22	23	Default	Alternate
00	--	--	--	--	24×80	24×80
02	--	--	--	--	24×80	24×80
03	--	--	--	--	24×80	R×C
7E	Rd	Cd	--	--	Rd×Cd	Rd×Cd
7F	Rd	Cd	Ra	Ca	Rd×Cd	Ra×Ca

The terms are as follows:

R×C

Screen Size defined by PC/3270 configuration

(R,C) = (24,80) , (32,80) , (43,80) , (27,132) or (62,160)

Rd

Rows in the default screen size mode

Cd

Columns in the default screen size mode

(Rd,Cd) = (24,80) , (32,80) , (43,80) or (27,132)

Rd*Cd <= R*C

Ra

Rows in the alternate screen size mode

Ca

Columns in the alternate screen size mode

(Ra,Ca) = (24,80) , (32,80) , (43,80) or (27,132)

Ra*Ca <= R*C

PC/3270 supports Query Replies. Make sure that the Query Reply of Implicit Partition returns the final screen size upon receipt of the BIND command.