A26

Explanation
A machine check interruption occurred on the only
online processor. The machine check interruption code associated with
the interruption is incorrect.  No recovery was possible.

System action
The system issues message BLW006W. The system
enters wait state X'A26'.

Operator response
To recover possible unrecorded machine check
error records, write a stand-alone dump. Retain the dump. Contact
hardware support.

Source
Machine check handler (MCH)