If you are experiencing illegible output in Run SQL Scripts like this
select BKHSYS as LPAR,
BKHMC as Class
from QUSRBRM.QA1AHS
where BKVOL = 'AS0047';
A column with a different CCSID setting may be to blame.
Then you can successfully use the case directive
select cast(BKHSYS as char(20) ccsid 37) as LPAR,
BKHMC as Class
from QUSRBRM.QA1AHS
where BKVOL = 'AS0047';
Coded Character Set Identifier used on every field you can display using command
DSPFFD FILE(QUSRBRM/QA1AHS)
Or you can try to setup correct Host Code Page in ACS Session Configuration
and restart Run SQL Scripts session
You can also check the JDBC Configuration (default) which Run SQL Scripts uses :