Access OS/390 3270 display sessions from OS/400 over SNA/APPN

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This is a short writeup of how to configure access to OS/390 3270 display sessions from OS/400 over SNA/APPN. A mandatory requirement is an already working SNA/APPN configuration between the two machines.

This article assumes OS/390 ADCD 2.10 being used.

Note: The configuration is somewhat complex, and this article is mainly a writeup to the point of apparently complete configuration. The desired functionality unfortunately does not work as expected: Logon is not possible.

Setting up VTAM

3270 display LUs are by nature dependent on a central PU to bring them up and down. This is a reminiscence of subarea (hierarchical) SNA. For that reason, VTAM must provide DLUS (Dependent LU Server) services.

Create a new member SYS1.LOCAL.VTAMLST(ASDLUS): 

ASDLMJ  VBUILD TYPE=SWNET
*
O390DLPU PU    IDBLK=056,
               IDNUM=03270,
               ISTATUS=ACTIVE,
               MODETAB=ISTINCLM,
               NETID=APPN,
               SSCPFM=USSSCS
*
O390DS02 LU    LOCADDR=02,
               DLOGMOD=SNX32702,USSTAB=USSS
O390DS03 LU    LOCADDR=03,
               DLOGMOD=SNX32702,USSTAB=USSS
O390DS04 LU    LOCADDR=04,
               DLOGMOD=SNX32702,USSTAB=USSS

Vary on this major node definition ASDLUS via console.

Setting up OS/400

  • Create the Display Devices:
crtdevhost devd(o390ds02) locadr(02) rmtlocname(o390ds02) ctl(o390dl) apptype(*eml)
crtdevhost devd(o390ds03) locadr(03) rmtlocname(o390ds03) ctl(o390dl) apptype(*eml)
crtdevhost devd(o390ds04) locadr(04) rmtlocname(o390ds04) ctl(o390dl) apptype(*eml)
  • Create the Controller Description referencing the Display Devices:
crtctlhost ctld(o390dl) linktype(*dlur) switched(*yes) appn(*yes) dev(o390ds02 o390ds03 o390ds04) sscpid(050000000059) lclexchid(05603270) swtdsc(*no) msgq(*sysval) pridlus(o390 *netatr) deppuname(o390dlpu)

Note: The SSCPID from my VTAM is 59, but crtctlhost wants a 05 in front. On the other hand, when setting it to the same value, VTAM complains IST1054I VALUE FOR SSCPID MUST BE BETWEEN 0 AND 65535. Not sure what this means.

Vary on the DLUR controller: 

vrycfg cfgobj(o390dl) cfgtype(*ctl) status(*on)

While there is no indication on the OS/390 console, you should get messages message in the qsysopr message queue that a CP-SVR-Pipe is now active.

Matching parameters

VTAM Parameter OS/400 Parameter Comment
idblk/idnum lclexchid
locaddr locadr
os390dlpu ctld, deppuname, ctl Switched node PU name
o390ds02 devd, rmtlocname Keep names equal, use 02 as template for more LUs
sscpname pridlus Take from VTAM config ATCSTRxx

Testing

The streml3270 command can be started with either a specific controller description, a device description, or a location name. For our testing, we can safely assume all LUs on OS/390 are currently free for use. 

streml3270 emldev(o390ds02)

You can enjoy a setup screen akin to strpasthr. Afterwards, the screen shows a logon greeting.

Weblinks

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