David, You may be disappointed. When a dataset on Primary is eligible for ML2 it will be migrated there directly during Primary space management.
Secondary space management will move datasets on Ml1 to ML2 if they have aged to their ML2 criteria. There is nothing that forces migration to take a detour to ML1. If you are DASD rich then I expect to see a fair amount of ML1 and ML2 activity during Primary Space Management when volumes occasionally dip below their space thresholds. If you have the traditional camel's hump CPU profile, then you would normally try an schedule Primary and secondary space management in one of the troughs of activity. If it is already running that way, and not driving peak utilization then I'd be wondering what the actual saving is. Ron > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of > O'Brien, David W. (NIH/CIT) [C] > Sent: Thursday, March 24, 2011 6:22 AM > To: [email protected] > Subject: Re: [IBM-MAIN] HSM Compaction question(s) > > John, Ron, Adam, > > Thanks for the feedback. Compaction has been turned off, ML1 to ML2 criteria > has been reduced. > Hopefully the performance folks will stop complaining about HSM, unlikely. > > To answer Ron's question about, 'why use ML1 at all'. We have abundant DASD, > tape drives not so much. I'd prefer to bundle data movement to ML2 to the > Secondary Space Mgt. window. I'm still cogitating whether or not that is a > valid concern. > > Regards, > Dave O'Brien > > > -----Original Message----- > From: Donnelly, John P [mailto:[email protected]] > Sent: Wednesday, March 23, 2011 10:59 AM > To: [email protected] > Subject: Re: HSM Compaction question(s) > > We are DASD rich and CYCLEs poor, therefore NOCOMPaction anything... > > John Donnelly > National Semiconductor Corporation > 2900 Semiconductor Drive > Santa Clara, CA 95051 > > 408-721-5640 > 408-470-8364 Cell > [email protected] > > > > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of > O'Brien, David W. (NIH/CIT) [C] > Sent: Wednesday, March 23, 2011 5:46 AM > To: [email protected] > Subject: HSM Compaction question(s) > > The system I inherited has compaction turned on for Dasdmigrate and > Dasdbackup. We notice spikes in CPU utilization during HSM Migration whether > it is manual or interval. Since we have DASD in abundance while CPU cycles are > sometimes in short supply, I'm considering turning off compaction to save on > overhead. > > My question to the group is whether the HSM users out there have compaction > turned on or not and if yes what is your COMPACTPERCENT setting? > Does anyone know of any downsides to turning off compaction, other than a > larger ML1 pool? > > David O'Brien > NIH Contractor > > ---------------------------------------------------------------------- > 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 > > ---------------------------------------------------------------------- > 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 > > ---------------------------------------------------------------------- > 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 ---------------------------------------------------------------------- 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
