The Informix precompiler provides a FREE statement that will release resources that are allocated to a prepared statement or to a cursor.
Once you have finished with a prepared statement, you would then use the FREE statement, for example:
move "INSERT INTO publishers " " &
"VALUES (?,?,?,?)" to stmtbuf
EXEC SQL
PREPARE stmt1 FROM :stmtbuf
END-EXEC
...
EXEC SQL
EXECUTE stmt1 USING :pubid,:pubname,:city,:state
END-EXEC.
...
EXEC SQL
FREE stmt1
END-EXEC