Changed DNS Server and now database connection is very slow

I changed our DNS server and when I disconnect the old DNS server our informix ids 11.5 instance takes up to 30 seconds to find the databases. If you use dbaccess it starts and when is is going to list the databases it stalls, the connect process and all query seem to run fine. We I have the old DNS server off line I can get good forward and reverse DNS lookups so the DNS for the os (debian linux) seems to be fine. I have not restart the Informix instance, it is a production system of a 24/7 contact center, so I don't want to restart without knowing that there might be a fix in it. Thanks Jackson

Bad news... There is currently no workaround (except eventually some network tweaking). The problem lies in the reverse DNS system call - gethostbyaddr() - The first time it runs it creates a cache of your DNS configuration. If you later change it, it has no way of knowing the change happened. So it keeps trying to talk to your previously configured DNS server. The delay is the time it takes to give up.... This can be showed with a simple C program. The cache will only be forgotten if the process calls another system function. Currently Informix doesn't do that. A mechanism would have to be implemented to allow the DBA to "ask" Informix to run that function. Note that other solutions like periodically call it, would be bad for performance. I've recently created a feature request for this. Note that this problem can affect any kind of server software (I've seen it with sendmail a few years ago). If your configuration of the resolver system included a first try with the files (/etc/hosts) you could try to workaround it by including all the client host IP address/names in the file. This is usually not advisable, but you may consider it a workaround until you can restart Informix Another possible option (and I'm getting completely out of my comfort zone here) could be trying to full the network layer to re-write the packet that are sent to the old DNS in a way that they're directed to the new one.... If you feel sufficiently annoyed by this you can also open a PMR (which will not solve your problem) and make sure your need is mapped to the feature I'm asked for. I could provide details. Regards. On Sat, Mar 26, 2011 at 6:07 PM, Jackson Thompson <jackson@valu-search.com>wrote: > I changed our DNS server and when I disconnect the old DNS server our > informix ids 11.5 instance takes up to 30 seconds to find the > databases. If you use dbaccess it starts and when is is going to list > the databases it stalls, the connect process and all query seem to run > fine. We I have the old DNS server off line I can get good forward and > reverse DNS lookups so the DNS for the os (debian linux) seems to be > fine. I have not restart the Informix instance, it is a production > system of a 24/7 contact center, so I don't want to restart without > knowing that there might be a fix in it. > Thanks > Jackson > _______________________________________________ > Informix-list mailing list > Informix-list@iiug.org > http://www.iiug.org/mailman/listinfo/informix-list > -- Fernando Nunes Portugal http://informix-technology.blogspot.com My email works... but I don't check it frequently...