topic Re: Analyze/Disk_Structure Utility in Operating System - OpenVMS

Analyze/Disk_Structure Utility

da1nonly1 — Thu, 07 Dec 2006 11:26:46 GMT

Hi,

I had a serious problem on one disk in a big VAX cluster (not Alpha). Some directories were not recognized by the operating system, as if they didn’t exist (just some not all the directories of the disk). I thought it might be a good idea to use first Analyze/Disk_Structure Utility to possibly detect and later fix the problem without a need to initialize the disk and load older data from backup tapes. The system administrator tried that but it didn’t work, it was hanging. I have these questions:
1) what can the cause for the above problem(some directories not recognized)?
2) I read that Analyze/Disk_Structure Utility must be used only when the disk is write locked, what does it mean? How can you do that?

Thanks for the answers.

Re: Analyze/Disk_Structure Utility

Steven Schweda — Thu, 07 Dec 2006 11:47:05 GMT

> [...] not recognized [...]

Actual commands and their actual output might
be more informative.

ANAL /DISK /REPAIR will write-lock the disk.
You don't need to do any write-locking
yourself. Write-locking the disk can annoy
users whose processes freeze for times up
to several minutes.

> didn t work, it was hanging

That could use a little more explanation,
too. Was there any disk activity? Did
CTRL/T show any I/O?

Re: Analyze/Disk_Structure Utility

Karl Rohwedder — Thu, 07 Dec 2006 11:50:09 GMT

That reminds me of problems we had some time ago, when user managed it to create directory files with versions greater than 1, leads to much confusion...

regards Kalle

Re: Analyze/Disk_Structure Utility

Andy Bustamante — Thu, 07 Dec 2006 13:31:31 GMT

Try $show error or $show device

You're looking for errors on the device, if a disk is failing it may begin to drop directories.

Andy

Re: Analyze/Disk_Structure Utility

Robert Gezelter — Thu, 07 Dec 2006 13:59:19 GMT

da1nonly,

First, I would recommend extreme caution. It is far to easy to turn a questionable corruption issue into a loss of data incident.

Before going too far, I would carefully review my situation. "Lost directories" can be caused by many problems, some of which are:
- disk errors
- accidental RENAME commands
- creation of directory files with version numbers other than 1 (as was mentioned earlier)

First, I would investigate precisely what is happening. A full image (or physical) BACKUP of the disk would also be a good idea.

Care and deliberateness are good things in this situation, it is easy to make things worse. If there is little experience dealing with this level of problem, I would recommend seriously considering outside assistance (disclosure: Yes, we have assisted clients with this type of situation for many years).

ANALYZE without the /REPAIR will also report the problems without modifying the disk.

More details are helpful.

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

Re: Analyze/Disk_Structure Utility

Jan van den Ende — Thu, 07 Dec 2006 14:18:44 GMT

da1nonly,

>>>
The system administrator tried that but it didn t work, it was hanging.
<<<

Until now I missed an important detail:
For how long was it hanging? Or, better formulation: are you SURE it was hanging. or only locking the disk (and every process using it), and very busy repairing?

Like Steven wrote, you do not need the /REPAIR for the analysys part.
But that WOULD be a very good indicator of the required time!

Measure how long it takes without /REPAIR, and then allow for 3-4 times WITH repair.

BTW, please DO make sure the process doing the repair is NOT writing something to the disk being repaired, like a nice report or some! I _HAVE_ come across that situation!

Proost.

Have one on me.

jpe

Re: Analyze/Disk_Structure Utility

GuentherF — Thu, 07 Dec 2006 14:59:18 GMT

If you want avoid the /REPAIR use at least /LOCK. This way the on-disk structure (or files system for the Unixers) does no tchange underneath the ANALYZE program and thus gives a consistent view on the disk volume.

/Guenther

Re: Analyze/Disk_Structure Utility

comarow — Fri, 08 Dec 2006 00:24:55 GMT

Do you have any idea what happened since last it worked?

Do you have a dir/full of any directory files?

Any hardware errors?

What kind of disk?

On what kind of controller?