The HSM migration exit (ARCMDEXT) is what we use to keep smaller datasets from migrating. You can find a sample in SYS1.SAMPLIB(ARCMDEXT).
We set the exit up to not migrate any datasets smaller than 10MB for 60 days and to not migrate datasets smaller then 5MB for 400 days. After 60 days we saw a daily 89% decrease in the number of datasets that were being migrated (67,226 down to 7,153) and a decrease of 17% in the number of recalls (2719 down to 2263). The CPU utilization for migration/recall reduced 45%. We did this without having to increase the size of the pools - since the datasets not migrating were so small. This was a win-win situation for us. Thanks....Rick -----Original Message----- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of Michael Wickman Sent: Monday, July 28, 2008 7:55 AM To: [email protected] Subject: Re: HSM Recalls Just curious how you select for migration base on size. Do you set special management class based on primary space at allocation time? Or are there HSM commands that help with this selection process? *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* Mike Wickman Technical Services email mwickman at waddell dot com *-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-* -----Original Message----- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of Ted MacNEIL Sent: Thursday, July 24, 2008 4:56 PM To: [email protected] Subject: Re: [IBM-MAIN] HSM Recalls >We do not migrate anything smaller than 5mb since the overhead of migrating them and having them recalled later was greater than the cost of just leaving them on disk! I mentioned this on IBM-Main many years ago. I was told I was full of s**t. Back then, it was any dataset a cylinder (.8 MB) or smaller. Now, I think even 5MB is probably small. Analysis is required, but the concept is sound. - Too busy driving to stop for gas! <font size="1"> <div style='border:none;border-bottom:double windowtext 2.25pt;padding:0in 0in 1.0pt 0in'> </div> "This email is intended to be reviewed by only the intended recipient and may contain information that is privileged and/or confidential. If you are not the intended recipient, you are hereby notified that any review, use, dissemination, disclosure or copying of this email and its attachments, if any, is strictly prohibited. If you have received this email in error, please immediately notify the sender by return email and delete this email from your system." </font> ---------------------------------------------------------------------- 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
