Using FLUSH QUERY LOGGING requests synchronously flushes all DBQL and TDWM caches across the whole system. All the PEs flush respective caches at the same time. When a FLUSH QUERY LOGGING request returns a success response to the client, the cache contents are written to their respective tables.
Note that submitting FLUSH QUERY LOGGING requests too frequently has the same negative performance impact as setting the DBS Control DBQL flag too low.
FLUSH QUERY LOGGING enables all the DBQL and TDWM caches to be flushed synchronously and does not return control to the client until all the caches have been flushed into the appropriate tables.