You've gotten a lot of answers and they are worrisome! Here's my 5 or 6 cents.
Yes, z/VM and Linux can go a very long time without being IPL'd/rebooted. Your applications may or may not. I would argue if they cannot, they need to solve the problem rather than clean it up with an IPL and/or reboot. If they need a reboot every weekend to clean up their memory problems, what happens if their volume doubles? Will they start rebooting every 3.5 days? We saw an app that started having very intermittent periods of weird delays after 5 or 6 weeks of uptime that was solved by an app recycle so they are now searching for a leak. I will add that I don't think I've ever seen an app leak problem affect Linux itself or for that matter VM itself - cycling the app or pkill -u appuser has been enough to clear up any memory issues. If someone asks your to recycle a server to solve an app problem , just say no ( Or more diplomatically, really??can't we try just recycling the app first?). The only ones I've seen that that was actually necessary on was when the OOM killer on Linux shot things, visible in the console. At that point reboot is inevitable and probably the server was short on memory to start with) . If you go more than a couple months on Linux or even on z/VM these days (and we all follow IBM ResourceLink Security for z/VM right?) , your patch policy is very generous or non-existent. I would say that we are at probably 5-6 VM IPLs per year to stay current (RSUs, releases, HW ucode), apply fixes we need (we find bugs, we apply fixes, we don't wait around to find the bugs that someone else already did) , and all security fixes. Linux is also averaging every other month for a reboot needed for kernel and/or glibc things that of course will require a reboot. Our challenge these days is to just coordinate those to same weekends so that there are change-free holiday weekends and system change free weekends so that those are available for application changes. PS - Our WMB (IIB) doesn't need weekly recycles as far as I've heard and we've been running that for probably 4 or 5 years. Its supporting some 70+ applications. These days when someone brags about uptime I'm not impressed. Watch the youtube from Share Seattle http://www.share.org/p/bl/et/blogaid=343 Yeah, it was z/OS, but is your tn3270 running encrypted and not subject to all the SSL bugs?! PPS to Sir Alan,: i need a card for the security weasel club, thanks :) Marcy -----Original Message----- From: Linux on 390 Port [mailto:[email protected]] On Behalf Of Will, Chris Sent: Wednesday, May 27, 2015 7:34 AM To: [email protected] Subject: [LINUX-390] Are weekly z/VM IPLs necessary? We have gotten in the habit of IPLing our z/VM and zLinux guests every Sunday during our standalone window. With the window shrinking and the need for 24/7 availability is it really necessary to IPL every week? If not what potential problems could we run into by not doing the IPL (memory leaks, logs filling etc.). This is in comparison to the Intel side of the shop (Red Hat, Windows) where they go months between IPLs. The only benefit I see is the opportunity to recycle WMB execution groups. Chris Will The information contained in this communication is highly confidential and is intended solely for the use of the individual(s) to whom this communication is directed. If you are not the intended recipient, you are hereby notified that any viewing, copying, disclosure or distribution of this information is prohibited. Please notify the sender, by electronic mail or telephone, of any unintended receipt and delete the original message without making any copies. Blue Cross Blue Shield of Michigan and Blue Care Network of Michigan are nonprofit corporations and independent licensees of the Blue Cross and Blue Shield Association. ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/ ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
