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OpenVMS Volume Shadowing and "SET DEVICE/PATH"

Craig W Post
Occasional Advisor

OpenVMS Volume Shadowing and "SET DEVICE/PATH"

Is it possible to issue a "SET DEVICE/PATH" command to a FC disk before it is shadowed and have the path be in effect or does the sysgen parameter "SHADOW=2" disable the "SET DEVICE/PATH" command?
12 REPLIES
Robert Gezelter
Honored Contributor

Re: OpenVMS Volume Shadowing and "SET DEVICE/PATH"

Craig,

As I understand your question, SET DEVICE/PATH should be independant of shadowing at that level.

Shadowing references are are to the DSA devices, SET DEVICE/PATH would affect the underlying DGA devices (based upon your use of FC disks).

I would have to research the shadowing manual to be sure. I would also accept correction from John, if he is following this thread.

- Bob Gezelter, http://www.rlgsc.com
Jan van den Ende
Honored Contributor

Re: OpenVMS Volume Shadowing and "SET DEVICE/PATH"

Craig,

I concur with Bob, with one (not important) remark: please specify your VMS version and patchlevel, as there have been some major enhancements in the last few of those, which may seriously influence the answer that applies to you.

Proost.

Have one on me.

jpe
Don't rust yours pelled jacker to fine doll missed aches.
Craig W Post
Occasional Advisor

Re: OpenVMS Volume Shadowing and "SET DEVICE/PATH"

Once a shadow device has been mounted, the "SET DEVICE/PATH" returns a %SET-E-NOTSET, error modifying $1$DGA1250:
-SYSTEM-E-NOSUCHPATH, specified path does not exist" error message so the Shadow Server will disable the "SET DEVICE/PATH" command for a device that was added to a Shadow Set. If you dismount the shadow disk, the command still will not work.
Craig W Post
Occasional Advisor

Re: OpenVMS Volume Shadowing and "SET DEVICE/PATH"

V7.3-2 with all the latest patches.
Robert Brooks_1
Honored Contributor

Re: OpenVMS Volume Shadowing and "SET DEVICE/PATH"

Please post the COMPLETE command you are issuing.

As has been correctly noted, the concept
of multiple paths for fibre channel devices is completely independent of whether or not said device is a shadow set member.

So, to answer the question -- Yes, you can
issue a $ SET DEVICE /PATH = /SWITCH command to a device before it is mounted (shadow set or not). Note that depending on the configuration of your cluster (if relevant) that the path *may* automatically switch again whilst the device is being mounted.

-- Rob (who spends much of his day writing code to deal with multipath, and is rather familiar with host-based volume shadowing)
Robert Brooks_1
Honored Contributor

Re: OpenVMS Volume Shadowing and "SET DEVICE/PATH"

Craig wrote . . .

Once a shadow device has been mounted, the "SET DEVICE/PATH" returns a %SET-E-NOTSET, error modifying $1$DGA1250:
-SYSTEM-E-NOSUCHPATH, specified path does not exist" error message so the Shadow Server will disable the "SET DEVICE/PATH" command for a device that was added to a Shadow Set. If you dismount the shadow disk, the command still will not work.

--

I cannot explain (yet) the behaviour that you observe, but I can say that your speculation as to *why* it is happening is not correct.

There is no notion whatsoever of "disabling"
commands done by the SHADOW_SERVER process.
Craig W Post
Occasional Advisor

Re: OpenVMS Volume Shadowing and "SET DEVICE/PATH"

Sorry, I am mistaken. I missed the fact that the second from the last digit was different on the paths for the two EVA controllers. The error message was correct and I was trying to set a non-existant path for one set of disks. My mistake!
Craig W Post
Occasional Advisor

Re: OpenVMS Volume Shadowing and "SET DEVICE/PATH"

I was mistaken and there was no problem.
Robert Gezelter
Honored Contributor

Re: OpenVMS Volume Shadowing and "SET DEVICE/PATH"

Robert,

My apologies, it slipped my mind that that was in your area.

Craig,

No problem. However, as Jan (and others would point out), it is good practice to award the points when closing the thread.

- Bob Gezelter, http://www.rlgsc.com
Craig W Post
Occasional Advisor

Re: OpenVMS Volume Shadowing and "SET DEVICE/PATH"

Sorry, this was the first time I have used this forum and did not understand about the points.
Robert Gezelter
Honored Contributor

Re: OpenVMS Volume Shadowing and "SET DEVICE/PATH"

Craig,

Not a problem. The points are just a Thank You for those of us who take the (uncompensated) time to answer colleagues questions. They also are a way of rating the responses (and getting people cute headgear).

- Bob Gezelter, http://www.rlgsc.com
Ian Miller.
Honored Contributor

Re: OpenVMS Volume Shadowing and "SET DEVICE/PATH"

info on the points system
http://forums1.itrc.hp.com/service/forums/helptips.do?#33

but don't get too hung up about it.
____________________
Purely Personal Opinion