1 out of 3 Transactions in DB2 fail with SQL 998, State 58005, error code 8, sub code 2
Apparently, this was the switch module. 
The RM OPEN STRING definition included: rmopenstring=db=mydatabase,uid=uuuuuu,pwd=pppp,,axlib=somelib
Once the value for axlib was supplemented with an extention, .so, the error has gone away.