problem with shared memory connections

hi all I'm having constant problems with shm connections in UDS 7.2x The error returned is -25588 - the appl process cannot connect to Online server server-name. It looks like Informix will allow so many shm connections before refusing a connection, but this seems to vary. If I change INFORMIXSERVER to a soc connection then everything is fine, but slower on a socket connection. Is there a config parameter or something that I should be looking for? any help or clues? I can supply the onconfig file if this will help many thanks Pete