How Virtual Terminals are determined by TPX.

Document ID : KB000054901
Last Modified Date : 14/02/2018
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Description:

How Virtual Terminals are selected by TPX?

Solution:

The ACT table APPLID (application) definition in TPXADMIN specifies the virtual terminal TYPE that is to be targeted when a session to the APPID is selected. However, if the APPLID is not defined in the ACT table, then TPX will assume defaults for the applid/application, and one of the defaults is to target UNIQUE virtual terminals for use by this applid/application.

So how does TPX select a virtual terminal?

When you sign on to TPX, you do so with a physical terminal, where the information about that physical terminal is displayed on the TPXMENU (upper, right of panel display). In most instances, when a session to an application is first selected, TPX determines the virtual terminal TYPE by checking to see if the APPLID for the session is defined in the ACT table-APPLID definition; if so, the TYPE=SHR/GRP/UNQ determines the target virtual pool, otherwise, the default UNQ virtual terminal pool is the target pool.

TPX next starts at the TOP of the virtual terminal node/pool definitions, walks thru the terminal definitions, and tries to find a virtual terminal that 1) is defined in the target pool (i.e. correct TYPE) and 2) does not already have a session (if target pool is UNQ) or a session to the applid (if target pool is GRP) on the virtual terminal. TPX will then use the BIND from the physical terminal to send over the virtual terminal; thus, if you log on to TPX as a MOD4, then most of your sessions to various applications will also be as a MOD4. In effect, the DLOGMOD (DLOGMOD=xxxxxxxx) definition in each virtual terminal is ignored/not queried.

However, the exception to this is as follows:

  1. If the ACT table-applid definition/fields: MODEL SENSITIVE = Y, EXTENDED
    DATASTREAM = Y., and/or MODE ENTRY OVERRIDE is set to a logmode value
    (i.e. not underscores).

  2. If the PROFILE level session detail and/or USERID level session detail has a MODENT name value specified (override to ACT-applid MODE ENTRY OVERRIDE field)

Any of the above noted fields will cause TPX to query the DLOGMOD field in each virtual terminal definition in order to find a match, and the virtual terminal node needs to have the correct number of MODELs 2/3/4/5/E defined.