Question & Answer
Question
What VTAM compatibility requirements must be met to run z/OS V1R10 Communications Server as an HPR-capable interchange node in a mixed subarea and APPN network?
Cause
z/OS V1R8 (and later) Communications Server provides additional information on existing APPN session establishment flows to identify when sessions cross from APPN into subarea (or vice versa) through an interchange node. These sessions are referred to as "interchange node sessions". The additional information is used by z/OS V1R10 Communications Server to separate interchange node sessions from APPN-only sessions by placing them on different RTP pipes.
Releases of z/OS Communications Server prior to V1R8 do not provide this additional information on existing APPN session establishment flows. As such, if an HPR-capable pre-V1R8 z/OS Communications Server (VTAM) node is involved in establishing interchange node sessions through a z/OS V1R10 Communications Server interchange node, the missing information might cause the V1R10 interchange node to assign these sessions to the wrong RTP pipe. When this occurs, the interchange node fails the session with sense code x'0897000A'.
Answer
All native and non-native HPR-capable VTAM APPN nodes must be be running z/OS V1R8 (or later) Communications Server (or have the necessary compatibility maintenance applied, see below) before you start any VTAM interchange nodes with z/OS V1R10 Communications Server.
Although the compatibility issue applies only when z/OS V1R10 is running as an HPR-capable interchange node, you and your business partners should upgrade any downlevel z/OS systems to V1R8 or later (or apply the appropriate maintenance) as soon as possible.
The following maintenance is available to bring older releases of z/OS Communications Server up to a level that is compatible with z/OS V1R10.
| Release | APAR | PTF |
| z/OS V1R7 | OA22854 | UA38026 |
| z/OS V1R6 | OA23005 | UA38066 |
Note: The PTFs for releases V1R7 and V1R6 is available only to customers who have an Extended Service Contract in place for those releases.
You will find a detailed explanation of the compatibility issue in:
- z/OS V1R10.0 Migration (from z/OS V1R9) GA22-7499-14, in section 7.1.15 SNA Services: Ensure compatible levels of VTAM for HPR sessions
- z/OS V1R11.0 Migration (from z/OS V1R9) GA22-7499-15, in section 7.1.15 SNA Services: Ensure compatible levels of VTAM for HPR sessions.
The V1R10 compatibility support is not available for all old releases of VTAM. If you are migrating one or more interchange nodes to z/OS Communications Server V1R10 or V1R11, there is still a risk that you could encounter compatibility problems even if all of your HPR-capable VTAMs are running z/OS Communications Server V1R8 or later. One example would be if you have business partners that attach to your network using APPN and one or more of their HPR-capable VTAMs do not have the necessary compatibility support.
To avoid all possible V1R10 or V1R11 HPR compatibility issues, a new function APAR is available for V1R10 (OA28332) and V1R11 (OA28727) that allows you to completely disable the new HPRSESLM function that causes the incompatibility issue by means of a new value for the HPRSESLM start option: HPRSESLM=DISABLED.
You must install this new function APAR, and specify HPRSESLM=DISABLED, on all HPR-capable V1R10 or V1R11 interchange nodes. HPRSESLM=DISABLED is only meaningful for interchange nodes, and can only be specified when a VTAM interchange node is started. That is, you cannot use the MODIFY VTAMOPTS command to set or change the DISABLED value for the HPRSESLM start option.
In base releases subsequent to V1R11, HPRSESLM=DISABLED should be coded on interchange nodes to completely disable the HPRSESLM function to allow this level of VTAM to coexist with older releases of VTAM.
For more information, see IBM Technote 1571664.
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Document Information
Modified date:
15 June 2018
UID
swg21367595