Re: Using 'kill -9'

Hi, nowadays killing a client application process will not crash the IDS server. However, under certain circumstances and without "onmode -z" you can have the situation where the server does not "notice" that the client is gone. This can result in a left-over session in the server, holding locks or possibly other resources. The circumstances are mainly that the connection is via TCP/IP and the server is waiting for data from the client. When the client is killed, it usually does not have a chance to tell the server about its imminent death, especially when killed with "kill -9". Due to TCP/IP implementation, the server does not get notified about the fact that the other end of the connection is gone as long as the server is only waiting for data to arrive. (The server gets an immediate error when it tries to send data to the client.) Often there is the TCP-KeepAlive feature enabled, which checks for connection health automatically and notifies the the application (i.e. the server) with an error even when it is only waiting for data. However, default timeout setting for TCP-KeepAlive usually is around 2 hours and then there are some retries before the error is actually produced and propagated. So the session would still hang around for about 2-1/4 hours ... Regards, Martin -- Martin Fuerderer IBM Informix Development Munich, Germany Information Management owner-informix-list@iiug.org wrote on 09.04.2005 04:15:21: > Hi All > I have been told by someone at work never to use 'kill -9' to kill Informix > programs (.4ge) without doing a 'onmode -z' on the session first. > > I am trying to find out exactly what happens and why this is necessary. > This is because I see people using 'kill -9' all the time and it hasn't > ever seemed to cause any problems. > > All I have been able to find out so far is the following from a web page of > the Washington Area Informix User group dating back to 1992. "Any user can > bring an Informix-Online instance down by killing an Informix process with > kill -9. Never kill a process with Kill -9 always use tbmode -z." > > When they refer to 'Informix process' in that paragraph, are they refering > to user programs (.4ge) or the oninit processes only? > > Is this something that used to be a problem but was fixed years ago? > > Thanks > Kevin > > -- > Message posted via http://www.dbmonster.com sending to informix-list