VTAM

The VTAM interface is the Com-plete communication channel to the SNA network. It maps the terminal I/O requests to the SNA protocol corresponding to a specific device (LU) type. LU0, LU1, LU2, LU3 and LU6.2 protocols are supported. On activating the VTAM Interface, Com-plete becomes a VTAM application LU known in the network by it's ACBNAME.

The VTAM interface is described under the following headings:

Defining and Activating the VTAM Application

Before the VTAM interface can be activated, the application must be defined (in SYS1.VTAMLST) and activated (VARY NET ACT,ID=acbname): 

name   APPL    APPC=YES/NO
       ,AUTH=(ACQ,PASS)
       ,ACBNAME=acbname
       ,PARSESS=YES
       ,MODETAB=mode_table
       ,SECACPT=ALREADYV
       ,DSESLIM=
       ,DMINWML=1
       ,DMINWMR=

where:

name specifies the network-unique name. If you do not code the ACBNAME parameter the network-unique name is used as ACBNAME. It must be identical to the name specified in the VTAMAPPL sysparm.
acbname specifies the minor node name assigned to this application program. This name must be unique within the domain in which the application program resides. If you do not code this operand, the network-unique name (the name of the APPL definition statement) is used as the ACBNAME.
mode_table specifies the name of a logon mode table to be used to associate each logon mode name with a set of session parameters. If you do not supply a logon mode table on the MODETAB operand, an IBM-supplied default logon mode table (ISTINCLM) is used. If you specify a table, both the table you specify and the default table are used. It is recommended to create a new mode table when new logon mode names are created or parameters on existing logmodes from the default table are changed.
APPC=YES is required to activate the LU6.2 (APPC) support.
AUTH=ACQ determines that Com-plete either the OPNDST macroinstruction with the ACQUIRE option or the SIMLOGON macroinstruction. (These macroinstructions enable Com-plete to initiate a session with a particular logical unit, e.g. a printer). If you code APPC=YES, this parameter defaults to ACQ and can be ommitted. If you code APPC=YES and AUTH=NOACQ, VTAM supplies an override of ACQ and issues a warning message.
AUTH=PASS is required if the PASS option of the ULOG utility is used, allowing VTAM to pass the session to another application. Otherwise the request will be rejectded with RC=20 (X'14') FDBK2=94(X'5E').
PARSESS=YES allows Com-plete to have multiple LU-LU sessions with the same session partner. PARSESS defaults to YES when APPC=YES. This option is required (explicitly or by default) when ULOG PASS is to be used or when Com-plete is used in conjunction with a session manager (as NET-PASS) in order to reduce the number of ACBs.
SECACPT=ALREADYV tells VTAM to build a BIND RESPONSE in order to allow "security"+"already verified" bits on incoming ATTACH requests.
DSESLIM maximum number of sessions between local and remote LU (default=2). must be > = DMINWML+DMINWMR.
DMINWML minimum number of sessions where the local LU is guaranteed contention winner.
DMINWMR minimum number of sessions where the remote LU is guaranted contention winner.

Notes:

  1. Check the NET-PASS sample exit NPEXIT07 on the distributed NET-PASS source library if NET-PASS is to provide the real LU-name of the terminal to Com-plete. The counterpart of this exit in Com-plete is activated automatically.
  2. SONSCIP=NO (default) should always be in effect, otherwise Com-plete will not be able to detect session failures and perform the termination processing for that user. Further attempts to re-logon to Com-plete will be rejected (user already logged on).
  3. See the description of APPLYMODs 29, 52, 53 and 69 for parameters affecting the VTAM Interface.
  4. Mode modename must be defined in a mode table before Transaction Routing to Com-plete is activated. CICS only uses its internal session characteristics (that may differ from those defined in the logmode table) instead of the VTAM mode definitions but they are required by Com-plete.
  5. Due to length differences between CICS transaction codes (4 bytes) and Com-plete program names (8 bytes), it is necessary to create a cross-reference table in Com-plete (see Com-plete Considerations) to match the transaction name trnm as known in CICS with the true Com-plete program name.
  6. The CICS CRTE transaction is also supported thus allowing CICS users to invoke Com-plete applications that do not have a TRANSACTION definition. However, corresponding URTETB entries must be coded also for these transaction names.

Generic Resource names

Any VTAM application program running on a VTAM that is connected to the z/OS coupling facility can use a generic resource name. VTAM keeps a map of the application programs that are members of each generic resource name. VTAM distributes incoming sessions that are initiated using a generic resource name among all members mapped to that name. A generic resource name may be specified by means of the VTAMGENERIC sysparm.

The following restrictions apply to generic resource names:

  • An application program can use one generic resource name at a time.

  • Generic resource members using the same generic resource name must have the same networkidentifier (NETID).

  • Generic resource names must be unique within a single network. If your network has multiple sysplexes, generic resource names must be unique throughout all sysplexes.

  • A USERVAR and a generic resource name cannot have the same name.

  • An ALIAS application program and a generic resource name cannot have the same name.

  • A name that is being used as an application program network name cannot be used as a generic resource name.

LOGMODES

Session parameters for the different device types or LU6.2 sessions are read directly from VTAM or it's libraries, eliminating redundant specifications and possible inconsistencies between specifications. This requires correct and entire specification of the parameters in the logmode entries, since these override the specifications in TIBTAB.