A20

Explanation
The system found a page in the fixed link pack
area (FLPA) that is not fixed.

System action
The system enters wait state X'A20'.
The system writes message IAR011W.

Operator response
If requested by the system programmer, obtain
a stand-alone dump. Attempt to reIPL the system without the FLPA.

System programmer response
Search problem reporting databases
for a fix for the problem. If no fix exists, collect a stand-alone
dump from the operator and contact the IBM® Support
Center.  Provide the stand-alone dump.

Source
Real storage manager (RSM)