Troubleshooting
Problem
During a processor reconfiguration a customer received IOS291I CONFIGURATION DATA COULD NOT BE READ ON PATH(4B50,C6) RC=21 TOKEN NED MISMATCH HAS BEEN DETECTED on their Ficon CTC links. Before that there was no attempt to vary paths offline, disconnect CTC links, etc. The customer thought it was NOT necessary
Symptom
IOS291I CONFIGURATION DATA COULD NOT BE READ ON PATH(4B50,C6) RC=21
TOKEN NED MISMATCH HAS BEEN DETECTED
Cause
Reason for the problem was in not varying paths offline prior to disconnecting cables
Environment
z/OS 1.13
Diagnosing The Problem
Diagnosis was based on the information provided by the customer
Resolving The Problem
According to a hardware SAPR guide for a zEC12 processor,
6. Plans are in place to account for any impact to other systems in
the environment which may be affected by the installation of the
zEC12. i.e. Deactivate any coupling link or CTC connections on other
connected systems prior to an upgrade or you may experience boxed
devices.
Account for other servers depending on STP messages for time
synchronization
This statement was in the draft for the z13 SAPR Guide but the guide
was cancelled due to changes in the HW assurance procedures (the IMPP
and Solution Assurance Checklists available on the Solution Assurance
website and Resource Link replaced the SAPR Guide for a z13.)
The reason for the recommendation is that
there are quite a few variables that might lead to different and/or
contradicting results. These are just a few of them:
- which side does POR,
- which side on the FCTC link owns an FCTC CU function,
- would an upgrade result in a change of a processor serial number,
- availability of a switch in the middle,
- time delays on switched links,
etc.
Hence, if an installation wants to accomplish changes cleanly,
it should follow the recommendation about configuring paths offline
(or doing VARY CU).
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Document Information
Modified date:
03 September 2021
UID
isg3T1023267