As you did not provide any criteria used in an index or in primary key, the database will perform a full scan of the database table (the UP TO 1 ROWS will stop once found some record, but if unlucky you could (and will, Peter's principle) get awful response time in production (and time out dumps, in development system, you have usually much less data available) -> Check with a SQL trace ST05.
Could you find another solution to check this field (Are you actually checking existence of at least one SO with this status ? ) thru domain value, or SAP provided index tables (similar to VRKPA for partner or VLKPA for deliveries)
At least only execute such SELECT only when user actually press the Execute icon (e.g. IF sscrfields-ucomm EQ 'ONLI'.)
NB: Also (let Customer) consider tools like BW for this kind of report.
Regards,
Raymond