performance threshold

hi i have a simple java program which writes and reads to and from an informix database in two different threads. i have about 40 transactions per second and i measure the time of each transaction. not real code: time = gettime(); con.execute(query); difference = gettime()-time; the problem i have is that the transaction time increases slowly (form < 10 ms to n*100ms) an this is slowing my whole application down. is it possible that the database is blocking my calls? by the way. i tried to use two different database connections or to set the lock mode to wait but nothing happened. does somebody have an idea where the problem is? thanks in advance! tom