Can we trust DB2 to determine the most efficient number of parallel processes in the configuration it runs in? My DB2 colleagues claim so.
Kees. -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Greg Dyck Sent: 29 September, 2016 16:43 To: [email protected] Subject: Re: Would HiperDispatch likely delay heavy multitasking job? On 9/28/2016 11:29 AM, Peter Hunkeler wrote: > Job in question is DB2 reorg utlility job which runs some 30 subtasks in > parallel runs for 2 hours. RMF III (60s intervals) shows that the job mostly > has a good workflow (80%+), is heavily using CP (often 80%-90%) and at the > same time is heavily delayed for CP (40%-60%). The job is seen to use up to > 230% CP. Using more subtasks is not always better. Within DB2 parallel utility processing there are points of serialization. Running with too many subtasks can actually degrade thruput due to contention rather than improve it. The contention can sometimes make RMF *think* there is more CPU delay than there really is because the subtasks frequently get suspended and resumed due to the contention. The only way to reduce the the CPU delay is to reduce the number of subtasks demanding CPU or to give the system more CPUs to dispatch subtasks on. Regards, Greg ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ******************************************************** For information, services and offers, please visit our web site: http://www.klm.com. This e-mail and any attachment may contain confidential and privileged material intended for the addressee only. If you are not the addressee, you are notified that no part of the e-mail or any attachment may be disclosed, copied or distributed, and that any other action related to this e-mail or attachment is strictly prohibited, and may be unlawful. If you have received this e-mail by error, please notify the sender immediately by return e-mail, and delete this message. Koninklijke Luchtvaart Maatschappij NV (KLM), its subsidiaries and/or its employees shall not be liable for the incorrect or incomplete transmission of this e-mail or any attachments, nor responsible for any delay in receipt. Koninklijke Luchtvaart Maatschappij N.V. (also known as KLM Royal Dutch Airlines) is registered in Amstelveen, The Netherlands, with registered number 33014286 ******************************************************** ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
