Hi Vlad,

Thank You for the answer. It could be an indication of a memory leak caused by an offending client application that failed to execute isc_dsql_free_statement after executing the statements. 

Anyone interested how I found out the offending client: selecting the records from the mon$statements table, observing that many statements' mon$state is 0 on statements that running too long from the same attachments.

Regards

Zsolt