This is probably a definition problem.

1. If you are using a USS command to log on, try logging on without it.
   If this corrects the problem, review the use of the USS command in z/OS Communications Server: SNA Resource Definition Reference and check the following items:

   • Is the terminal a non-SNA 3270?

     If it is, does the USS command include a USSPARM macro for the logmode?

     If so, VTAM® ignores the logmode name from the terminal definition statements and uses its own default BIND image instead.

   • Does the USS command establish a default logmode name?

     If so, the default name overrides the name in the terminal definition statement.

2. If this is not a USS command problem, check to see whether the PSERVIC operand of the MODEENT macro is coded correctly. z/OS Communications Server: SNA Resource Definition Reference explains how to do this.
   • Are primary and alternate sizes coded correctly?
   • For screen switching, is BINPRESZ coded correctly as X'7F'?
3. If you have not identified the problem, look at the BIND that is sent.This is shown in a VTAM buffer contents trace of the logon.
   • If the BIND image is not what you expected, check the LU definition statement for an incorrect MODETAB or DLOGMOD parameter.
   • If no logmode table or DLOGMOD operand is specified, no PSERVIC is passed to the TSO/VTAM logon exit routine. In this case, TSO/VTAM issues an INQUIRE DEVCHAR macro and VTAM indicates that the terminal is a logical unit. TSO/VTAM then uses the SCRSIZE operand found in TSOKEY00. The default value for SCRSIZE is 480 (12 rows and 40 columns).
4. If you have not resolved the problem, go to Reporting the problem to IBM.