The problem is described by reason code ‘4’. Message SQL0752 in QSQLMSG lists the reason codes.
“4 — The connection is locked by another invocation of Interactive SQL, or there is a level mismatch between the Interactive SQL product and the DB2 UDB for iSeries product.”
You already have a connection to the database in your job. STRQMQRY tries to establish a new connection. I don’t believe you’ll be able to do execute a Query Management Query (*QMQRY) in a stored procedure. However, chould you move the logic from the *QMQRY directly to the stored procedure?