I can't quantify, but I can supply empirical evidence. In my last job we brought up DB2 V8 under z/OS 1.4 (running in 64-bit mode) and it was really slow compared to V7.
The reason is pretty simple - the FLEX emulation has to perform over twice as many instructions to simulate a 64-bit operation as the corresponding 31 bit (or 32 bit, thinking register arithmetic) operation. Remember, current releases of FLEX and associated hardware are 32-bit machines. (I have heard rumors that FLEX has been compiled and tested on 64-bit hardware, but nothing has been released to The Real WorldT.) Off the top of my head, I would expect at least a 50% reduction in throughput, and probably even more, in 64-bit mode. I think this performance issue is a big reason why IBM has not allowed operating systems that require 64-bit architecture to be licensed to FLEX systems for commercial customers. (It is licensed to PWD members.) This also has put small z/OS and z/VM operations into a bind - no place to grow except to higher-priced hardware if they want to go beyond z/OS 1.4 (and z/VM 4.4, I think). Hopefully IBM will take (and is taking) steps to help these customers and that someday, in the near future, something will be announced. Later, Ray > -----Original Message----- > From: IBM Mainframe Discussion List > [mailto:[EMAIL PROTECTED] On Behalf Of Jim McAlpine > Sent: Tuesday December 06 2005 06:25 > To: IBM-MAIN@BAMA.UA.EDU > Subject: DB2 Version 8 on a Flex-ES box. > > Does anyone have any experience of the above and if so have > you noticed any performance degradation because of 64 bit > instruction emulation on 32 bit instruction hardware. Better > still, can anyone quantify it. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
