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10-01-2012 09:59 PM - edited 10-01-2012 10:00 PM
All our systems consist of clusters containing Alpha and Integrity nodes running VMS 8.3 & 8.4, respectively. Some run just V8.4.
The disks do not have any special caching set up; whatever VMS defaults to is what they have.
Consequently the XFC cache looks something like this:
$ show memory/cache System Memory Resources on 2-OCT-2012 14:55:56.63 Extended File Cache (Time of last reset: 5-SEP-2012 09:13:30.09) Allocated (GBytes) 15.57 Maximum size (GBytes) 15.99 Free (GBytes) 0.25 Minimum size (GBytes) 0.00 In use (GBytes) 15.32 Percentage Read I/Os 99% Read hit rate 98% Write hit rate 0% Read I/O count 4179894929 Write I/O count 31061933 Read hit count 4099161149 Write hit count 0 Reads bypassing cache 5819 Writes bypassing cache 21744798 Files cached open 849 Files cached closed 63640 Vols in Full XFC mode 0 Vols in VIOC Compatible mode 9 Vols in No Caching mode 0 Vols in Perm. No Caching mode 0 $
You'll notice all volumes are in "VIOC Compatibility Mode".
Is there any performance improvement to be had by forcing these disks to mount in "Full XFC mode" instead? Any potential problems?
Solved! Go to Solution.
10-02-2012 07:53 AMSolution
Steve, why always the levels of indirections even for simple stuff. Just answer the question already?
"Have you checked the VMS FAQ?"
So you did, and found it right? Why not add just a pointer and/or the result?
Google for : openvms faq "VIOC Compatible Mode" leads nowhere in a hurry.
Google for "openvms faq" first leads to http://www.openvms.compaq.com/faq/openvms_faq.html which is garbage.
It does point to http://www.hoffmanlabs.com/vmsfaq/ which is useful
in the end you wrote "VIOC Compatibility Mode".
Well that's what I picked up for google string and it made for a miserable hunt.
"VIOC Compatible mode" is easy hunting.
9.10 If my disks are shown as VIOC Compatible, am I using XFC? Yes, you are using XFC caching. Disks that are using XFC caching use communication and coordination protocols that are compatible with the older VIOC caching implementation. With the initial implementation of XFC on OpenVMS, you can use the command SHOW MEMORY/CACHE to see no disks reported in full XFC mode; all disks shown will be listed in "VIOC Compatable Mode". If you have the OpenVMS system parameter VCC_FLAGS set to 2 and are using OpenVMS Alpha V7.3-1 or later, or are using OpenVMS Alpha V7.3 with the VMS73_XFC V2.0 ECO kit or later or with the UPDATE kits, you are using XFC. Another confusion: the XFC product version is and remains V1.0 in all released configurations, please do not confuse the internal XFC product version (displayed by various commands) with the version number associated with the various ECO kit(s). XFC V1.0 does not permit volumes to enter full XFC caching, as displayed by the "Vols in Full XFC mode" portion of the DCL command SHOW MEMORY/CACHE output.
10-02-2012 05:13 PM
Re: VIOC Compatibility Mode, should I turn it off?
The OpenVMS FAQ doesn't really answer my question, but pointing out that the text was "VIOC Compatible" rather than "VIOC Compatibility" did help. Google search brings up the VMS 7.3 OpenVMS System Manager's Manual so I ignored that and found the relevant section in the VMS 8.4 manual.
Here are that manual's comments about the output of the SHOW MEMORY/CACHE command, which I found rather enlightening ...
Vols in Full XFC mode
Reserved for future use by HP. Should be 0.
Vols in VIOC Compatiblode mode
The number of volumes being cached by XFC that are using the VCC caching protocol. As of OpenVMS Version 7.3, XFC uses only VCC caching protocol.
In other words these parts of the SHOW MEMORY/CACHE display are essentially misleading as there is no such thing as "full XFC mode". (Not as far as customers are concerned, anyway! Yes I suppose it exists in the system and can be enabled if you know how, but the number of XFC-related patches that have come out over the years would indicate that such a step is not to be taken lightly.)