Negotiation when VTAM owns the SLU

When VTAM® owns the SLU for the session, the SLU can begin negotiation when it sends the control vector X'66'. The control vector indicates whether compression is prohibited or required. If compression is required, the COMPRES operand on the MODEENT macroinstruction must indicate that compression is required.

When sending the BIND(RSP), the SLU negotiates no compression if any of the following conditions occur:

The BIND does not request compression.
PROHIB or SYSTEM was specified in the control vector X'66'.
The CMPVTAM start option is set to 0, which indicates no compression.

Note: When compression is negotiated from the SLU side, the CMPAPPLI and CMPAPPLO operands are not used.

If none of the previous conditions occur, the SLU requests compression levels. The PLU-to-SLU compression level is the lower of the values set on the CMPVTAM start option or the requested PLU-to-SLU compression level passed on the BIND. The SLU-to-PLU compression level is the lower of the values set on the CMPVTAM start option or the requested SLU-to-PLU compression level passed on the BIND.