Filesystem and logical names

[geir_2]

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?

[Joseph Huber_1]

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 ...

[Ian Miller.]

" 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.

[geir_2]

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

[Hein van den Heuvel · Accepted solution]

> 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.

[Hein van den Heuvel]

>> 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.

[Robert Gezelter]

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

[Marc Van den Broeck]

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

[geir_2]

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.]

[Antoniov.]

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