Calling DB2 statement through a unix shell

I am looking to execute a DB2 command in the background through
shell .

Shell script:

db2 -tvf updatecust.sql &

Within updatecust.sql, it established a connection to the db and
executes an update statement. Using the & causes the statement to
fail. I have tried quotes and the exec statement.

Error: DB21018E A system error occurred. The command line processor
could not continue processing.

Removing the &, and the script runs as expected.