Thanks for the comments. > to set DB2 memory management to "automatic" to let it size itself based on the Linux configuration. Which can be interpreted as, with STMM set (fully) on, DB2 will try to use 85% of configured memory (if it needs it ofr not). Then it's back to guessing how much is really needed. After the initial wag of sizing, (hopefully it is on the conservative side), it finding the point where there is enough memory to run at the peak loads and have a little to spare and not too much to cause excessive VM paging. I am a little surprised that we are not mentioning response times for DB requests during peak periods, or throughput as metrics to help evaluate memory needs and the tools/ways to help collect this data. Thx
Rob van der Heij <[email protected]> Sent by: Linux on 390 Port <[email protected]> 02/05/2010 10:03 AM Please respond to Linux on 390 Port <[email protected]> To [email protected] cc Subject Re: A Question on Sizing z/VM Linux Guests On Fri, Feb 5, 2010 at 4:26 PM, Sterling James <[email protected]> wrote: > I realize that it would not be a apples to apples comparison, but is there > a similar discussion about sizing guests that are running DB2? With STMM > on? And the "Be ware!"s? Does DB2 have instrumentation that can tell you > how it's using memory and indicate "good" value. I am aware the STMM is > suppose to do that automatically, but I am suspicious of it's assumption > since it does know account for running under zVM. The DB2 folks will prefer to compare oranges and oranges, since IBM is very strict on not involving competitors in comparisons. :-) You're right, with DB2 there's also shared memory between threads that lives in page cache. So you should expect the page cache to be fairly large on such a system. I did find that many DBA's seem to set DB2 memory management to "automatic" to let it size itself based on the Linux configuration. I don't think DB2 needs to be aware that Linux runs on z/VM. If the automatic memory management works well, it would not be a bad approach that you'd only have to size the virtual machine to make it happen. We recently had conversations with the DB2 people discussing changes in DB2 to improve behavior for low-utilized servers with Linux on z/VM. I'm supposed to get my hands on the fix pack that implements those RSN and be able to kick the tires. I'm also interested to investigate the tuning options and instrumentation. Rob -- Rob van der Heij Velocity Software http://www.velocitysoftware.com/ ---------------------------------------------------------------------- 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 ----------------------------------------- Please consider the environment before printing this email and any attachments. This e-mail and any attachments are intended only for the individual or company to which it is addressed and may contain information which is privileged, confidential and prohibited from disclosure or unauthorized use under applicable law. If you are not the intended recipient of this e-mail, you are hereby notified that any use, dissemination, or copying of this e-mail or the information contained in this e-mail is strictly prohibited by the sender. If you have received this transmission in error, please return the material received to the sender and delete all copies from your system. ---------------------------------------------------------------------- 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
