topic Re: Filesystem and logical names in Operating System - OpenVMS

Filesystem and logical names

geir_2 — Tue, 06 Sep 2005 06:25:00 GMT

Hi,

For most of you I have simple questions. What's the connection between logical names and phisical disk?

A system can contain many hardisk, but the logical names ties the physical disk together in a logical structure. A logical names can also contain logical names. Is it a simple way the see the connection between physical disk and logical names?

Re: Filesystem and logical names

Joseph Huber_1 — Tue, 06 Sep 2005 07:19:28 GMT

Would You explain or formulate a bit more precise ? There is no such thing like "logical names ties the physical disk together in a logical structure" .
In principal there is no way to find logical names from a given physical disk specification.
The only way I could imagine is to search for the device in all logical names like this:
pipe show logical * | search sys$pipe DKA100
Then You get all logical names containing the device DKA100.

However there are always certain logical names defined for each mounted VOLUME, which is
DISK$label where label is the disks volume label.

Now this is simple in the case of directly attached single volume disks, where You have a 1-to-1 relation between disk$label and the device.
Next step are bound volume-sets: here the logical name points only to the first volume of the set, but a
show device disk$label
show all devices pertaining to this volume set.

You see, there is no 1-to-1 relation, and it becomes even more difficult for shadow-sets and SAN disks ...

Re: Filesystem and logical names

Ian Miller. — Tue, 06 Sep 2005 07:35:45 GMT

" pipe show logical * | search sys$pipe DKA100
Then You get all logical names containing the device DKA100."

You are searching the logical names in the tables listed in your current dcl logical name table search list (usually process, job, group, system) not all logical name tables. For example there may be logical names defined in other group tables which refer a particular disk.

Re: Filesystem and logical names

geir_2 — Tue, 06 Sep 2005 07:41:24 GMT

Hi,
thank for the answer, but I connot find pipe, | and sys$pipe on my system. But I'm sure it would be a great advantage to use it.

Is it shell script? It sounds like UNIX.

Geir

Re: Filesystem and logical names

Hein van den Heuvel — Tue, 06 Sep 2005 07:45:23 GMT

> What's the connection between logical names and phisical disk?

There is none, other then in the mind of the beholder, and in the script that defined them. The main purpose of logical names is not to connect, but to seperate. To seperate the knowledge in the application to 'logical' names from the actual implemenation on physical entities.

>> logical names ties the physical disk together in a logical structure

As soon as you try to capture a physical structure with logical names you will find that you are setting yourself up for meedless restrictions. Logical names should remain a convenience, a seperation layer, and can not double up as structure reference.

>> A logical names can also contain logical names

As in: logical name "master_file" = master_data:[2005-data]master.dat, where master_data is a logical name defining the actual device? Yes that is good and command practice, but somewhat redundant in some cases.
While you define 'marter_file' you may or might not want to pick up the real master_data device, depending on the application. In the middle of a single batch job may prefer not to see a redefined master_data.

>> it a simple way the see the connection between physical disk and logical names?

$pipe show log /all | sea sys$pipe "= ""''f$getsyi(""NODENAME"")'$"

Unlike (soft)links there is no disk-permanent structure to define logical names.

Whatever the command files and/or command lines defined it to be, that's what it is.
Often a lot of that is hardcoded in files called something like: "sys$startup:*logic*.com"

You may find them as 'device level', 'directory level', 'application level' or 'file level'. It all works. Consistency within your application is the most important. Flexibility comes right next after that.

hth.
Hein.

Re: Filesystem and logical names

Hein van den Heuvel — Tue, 06 Sep 2005 07:49:49 GMT

>> I connot find pipe, | and sys$pipe on my system

Ah, a reply (or two :-) snuck in while I was typing/getting a morning coffee refresh.

The PIPE command is 'newish' (as in less than 10 year old :-) in VMS. I don't recall when it came to be, but I have it on my old 7.1 config.

You must be running OpenVMS 6.x or such?
Please consider upgradign and enjoiying a host of improvement, not to mention that you'll be able to enjoy speak the same language as your peers/support persons.

Hein.

Re: Filesystem and logical names

Robert Gezelter — Tue, 06 Sep 2005 07:50:02 GMT

Geir,

A logical name may point to:

- a physical disk
- a volume set
- a directory on a physical disk
- another logical name

Doing a SHOW LOGICAL on the name will show the iterative translation (SHOW TRANSLATION will not).

As an example, do a $ ASSIGN SYS$SYSROOT: DISK

If you then do a SHOW LOGICAL DISK, you will find that DISK translates (iteratively) to the system common and system specific directories on your system disk.

Can you be more specific, I am not clear on exactly what you are asking.

- Bob Gezelter, http://www.rlgsc.com

Re: Filesystem and logical names

Marc Van den Broeck — Tue, 06 Sep 2005 08:02:58 GMT

Geir,

logical names imho can refer to anything, not only to disc or file related matters. You can put a value (true, false, some timeout, ...) in it.

It is some kind of variable that Vms translates to its value.

The advantage is that you have logical name tables on several levels (process, job, system, ...)

Rgds
Marc

Re: Filesystem and logical names

geir_2 — Tue, 06 Sep 2005 08:22:05 GMT

Hi,
thanks for the answers. I know that my system is old, but it's impossible to upgrade the system, since it's in use 24 hours.

I'm not so familiar with OpenVMS, and that's the reason that I have problems to describe the problems exactly.

As far as I understand it's a root directory on each disk eg. dka100:[000000], dka200:[000000] etc.

But what it's the explantaion of the following commands? And how do I define logical name in simular ways? Thanks.

OpenVMS> show log sys$sysroot
"sys$sysroot" = "osfs1$dka0:[sys0.]"
= "sys$common:"
1 "sys$common"="os3fs1$dka0:[sys0.syscommon.]

Re: Filesystem and logical names

Antoniov. — Tue, 06 Sep 2005 08:50:16 GMT

what it's the explantaion of the following commands? And how do I define logical name in simular ways? Thanks.

OpenVMS> show log sys$sysroot
"sys$sysroot" = "osfs1$dka0:[sys0.]"
= "sys$common:"
1 "sys$common"="os3fs1$dka0:[sys0.syscommon.]

sys$sysroot is a logical name with searching list; it means when you refer to sys$sysroot: as device, system search at first time into osfa1$dka0:[sys0.] directory and then into sys$common: (that's another logical name).
You can define this kind logical name with
$ DEFINE "<1stDef>,<2ndDef"
For example:
DEFINE MYLOG MYDISK0:[DIR1],MYDIS100:[DIR2]

Antonio Vigliotti

Re: Filesystem and logical names

Robert_Boyd — Tue, 06 Sep 2005 08:51:37 GMT

The explanation at the 1st level is that there is a rooted search list logical name SYS$SYSROOT defined that points to the system software root that your system is booted from. This list on the system you did the command is made up of 2 parts: the system specific component which is listed first, and the "common" component which is listed second.

In your case, the 1st element, the system specific component is pointing to physical device osfs1$dka0: with root [sys0]. The "common" element, the 2nd one in the list is pointing to sys$common which translates to "physical" device osfs3$dka0: and root [sys0.syscommon] which may actually translate to the same as root [vms$common] depending on the vintage of your system. It is possible that osfs1$dka0 actually translates to something else (more fundamental). The name osfs3$dka0 may also translate to something more fundamental. If these 2 names are actual physical device names, then you have part of your system files residing on one disk drive and part of them residing on another.

Robert

>>But what it's the explantaion of the following commands? And how do I define logical name in simular ways? Thanks.

OpenVMS> show log sys$sysroot
"sys$sysroot" = "osfs1$dka0:[sys0.]"
= "sys$common:"
1 "sys$common"="os3fs1$dka0:[sys0.syscommon.]

Re: Filesystem and logical names

Hein van den Heuvel — Tue, 06 Sep 2005 09:00:01 GMT

RTFM!
Time to go Read The Fine Manuals my friend!
Be on the looked for 'rooted directories' and 'concealed' logical names. Enjoy!

(and don't forget to try the $HELP command)

User guide on directories

http://h71000.www7.hp.com/doc/731FINAL/6489/6489pro_008.html#directs_ch

Users guide on logicals

http://h71000.www7.hp.com/doc/731FINAL/6489/6489pro_026.html#lognames_ch

Guide to files on 'rooted directories'

http://h71000.www7.hp.com/doc/731FINAL/4506/4506pro_018.html#16_rooteddirectorysyntaxapplic

btw... since I am replying anyway, If you do not have pipe, then you may want to use a temporary file. In our example:

$ show log /all /out=logicals.tmp
$ sea logicals.tmp "= ""''f$getsyi(""NODENAME"")'$"

Hein.

Re: Filesystem and logical names

David Jones_21 — Tue, 06 Sep 2005 09:51:04 GMT

"The main purpose of logical names is not to connect, but to seperate. To seperate the knowledge in the application to 'logical' names from the actual implemenation on physical entities."

It depends upon your perspective. If you have a program that does operations on an abstract 'tape' device, you still need to assign (i.e. connect) a real device to the logical name for the program function. Logical names provide the connections that allow you separation applications from physical entities.