Although we don't use a VTS, I thought an observation may help. Someone on this list already mentioned but indulge me. We use an ATL and it takes at least 2 minutes for a tape to be mounted. Any chance that something is dumping the vts data set to tape almost instantly and then in order for the tape data set to be reloaded, the physical cartridge has to be retrieved? The comment about the 3 minutes clicked almost instantly with me, as I mentioned earlier the time is the approx. duration we have to wait for a physical tape to load. Just my 2 cents. Steve
-----Original Message----- From: The IBM z/VM Operating System [mailto:ib...@listserv.uark.edu] On Behalf Of Suleiman Shahin Sent: Sunday, May 10, 2009 9:15 PM To: IBMVM@LISTSERV.UARK.EDU Subject: Re: VTS issues What you described sounds similar to what I'm experiencing. I have not been able to find any commands or sources of information on cache or real tape fragmentation. But I know how many volumes we have and the number of physical tape carts used. The ratio is about 220 virtuals to each 3590 (10GB tapes) tape. What you described as fragmentation of virtual volumes is probably taken care of by "reclamation" which consolidates lightly used tapes into others and keeps a set minimum on each physical tape. In the light of what you said, I believe cache is pretty well used up and to mount a new scratch some other volume has to be moved out. Very good info. Thank you very much and have a great week. Suleiman Shahin ---------------------------------------- > Date: Sun, 10 May 2009 19:28:03 -0500 > From: mike.wal...@hewitt.com > Subject: Re: VTS issues > To: IBMVM@LISTSERV.UARK.EDU > > We use a Sun/STK VTS (shared with z/OS). Scratch mounts are nearly > instantaneous (unless z/OS isn't responding due to high batch workloads). > > Recalls times vary depending upon whether the virtual tape was in cache, > or on 'backing store' (i.e. offloaded to real physical tapes within the > VTS robotics). If the recall is in cache, the mount is also > near-instantaneous. > > But recalls of tapes on backing store can take a long time, depending on > how busy the real tape drives are (many z/OS systems here can place a > stress load on the VTS), how full cache is (the VTS may have to offload > some virtual tapes to real tapes to make room for your recalled file), and > other factors. > I suspect that those same effects will be pretty consistent across all > brands of VTS manufacturers that use cache for virtual tapes, and real > tapes for offloading as backing store. > > Do you have any commands to display cache utilization, virtual and real > tape drive utilization, and real tape 'fragmentation'? It might be time > to "merge/purge" backing tapes, running a vendor provided utility to copy > unexpired virtual tapes from fragmented real tapes onto fresh real tapes, > more fully filling the new real tapes, and freeing up whole real tapes for > re-use. > > Mike Walter > Hewitt Associates > > > > > "Suleiman Shahin" > > Sent by: "The IBM z/VM Operating System" > 05/10/2009 06:55 PM > Please respond to > "The IBM z/VM Operating System" > > > > To > IBMVM@LISTSERV.UARK.EDU > cc > > Subject > Re: VTS issues > > > > > > > Mainly for recall of existing files. But also mount times for scratches > can take 3 minutes. > > Thanks. > > Suleiman Shahin > > > > > > > > ---------------------------------------- >> Date: Sun, 10 May 2009 17:40:12 -0500 >> From: mike.wal...@hewitt.com >> Subject: Re: VTS issues >> To: IBMVM@LISTSERV.UARK.EDU >> >> Mount times for scratch tapes or recall of existing files? >> >> Mike Walter >> > > _________________________________________________________________ > Hotmail(r) has a new way to see what's up with your friends. > http://windowslive.com/Tutorial/Hotmail/WhatsNew?ocid=TXT_TAGLM_WL_HM_Tu torial_WhatsNew1_052009 > > > > > > > The information contained in this e-mail and any accompanying documents may contain information that is confidential or otherwise protected from disclosure. If you are not the intended recipient of this message, or if this message has been addressed to you in error, please immediately alert the sender by reply e-mail and then delete this message, including any attachments. Any dissemination, distribution or other use of the contents of this message by anyone other than the intended recipient is strictly prohibited. All messages sent to and from this e-mail address may be monitored as permitted by applicable law and regulations to ensure compliance with our internal policies and to protect our business. E-mails are not secure and cannot be guaranteed to be error free as they can be intercepted, amended, lost or destroyed, or contain viruses. You are deemed to have accepted these risks if you communicate with us by e-mail. _________________________________________________________________ Hotmail(r) has a new way to see what's up with your friends. http://windowslive.com/Tutorial/Hotmail/WhatsNew?ocid=TXT_TAGLM_WL_HM_Tu torial_WhatsNew1_052009
