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VMS Image backup

 
Shriniketan Bhagwat
Trusted Contributor

Re: VMS Image backup

Hi,

Image BACKUP archives only the occupied blocks (i.e. space occupied by the files) but not the free space as in case of physical BACKUP. Hence in your case you can backup the disk of capacity 250GB (containing occupied space 100GB) on to the 150GB capacity disk.

If you are using /IGNORE=INTERLOCK qualifier (online BACKUP), then there will be the slight difference between the data in the saveset as compared to the actual file which are locked during BACKUP. To have the consistence copy of the files, it is recommended to perform the offline BACKUP i.e. after business hours when the less activity on the disk is happening.

Regards,
Ketan
Shriniketan Bhagwat
Trusted Contributor

Re: VMS Image backup

Hi,

Some details about the /IGNORE= INTERLOCK qualifier.

/IGNORE= INTERLOCK qualifier processes files that otherwise could not be processed due to file access conflicts. Use this option to save or copy files currently open for writing by other applications. This qualifier instructs BACKUP save or copy operation to override restrictions placed on files such as interlocks. File system interlocks are expressly designed to prevent data corruptions, and to allow applications to detect and report data access conflicts. Use of the INTERLOCK keyword in BACKUP overrides these file data integrity interlocks. The data that BACKUP subsequently process/archives can then contain the difference as compared with that of open files.

Regards,
Ketan
Jan van den Ende
Honored Contributor

Re: VMS Image backup

Chandra,

>>>
So shall I estimate in multiple of that time which comes
around 9-10 Hrs for 100Gb of data. It is not possible to take downtime of system for that much of time since disk is online and used for critical public application.
<<<

So, now is the time to get YOUR knowledge of YOUR system to work.
- What account is running BACKUP? Using a dedicated account with parameters optimised for Backup for YOUR environment (if you are not already doing that) can make a big difference. I have not yet seen what disk config you have, but take into account that SAN controllers react quite unfavorable to the "older" optimisation suggestions!
- Does your data have (easily identifiable) big ( say, at least 30 % ) parts of rarely or never changing data? Then you can make (at least 2) BACKUPs of those files. Store them SAFELY. And then
$ SET FILE /NOBACKUP for those files.
But remember that when you need a restore, you must get those from their own backups.
And if you have to modify any of that, you need to refresh their BACKUPs.
For that action, do NOT forget /IGNORE=NOBACKUP in that BACKUP command.
- The previous can be made much easier if you can split the stable and the volatile data over different drives. (Logical Names can be a big help in that!). Now you make regular backups of the "volatile" drive, and only after changes, of the "stable" data drive.

hth

Proost.

Have one on me.

jpe
Don't rust yours pelled jacker to fine doll missed aches.
Shriniketan Bhagwat
Trusted Contributor

Re: VMS Image backup

Hi,

In this case for the long run, to reduce the BACKUP window, you can prefer the combination of image and incremental backup strategy.

Regards,
Ketan
Art Wiens
Respected Contributor

Re: VMS Image backup

"It is not possible to take downtime of system for that much of time since disk is online and used for critical public application."

If it's "critical", then some money needs to be spent on additional disk storage and software licensing resources - set up volume shadowing. A disk member containing the data can then be removed from the shadow set (leaving the application available) for backup purposes.

Uptime has associated costs.

Cheers,
Art
Stanley F Quayle
Valued Contributor

Re: VMS Image backup

100 GB of data might not fit in a 150 GB disk.

A 1-byte file will occupy a number of disk blocks equal to the cluster factor.

Another reason is the maximum number of files on the disk, which is related to the cluster factor.

Both of these values are determined when the disk is initialized. In VMS versions prior to V7.2, there was a set formula for the cluster size. On big disks, that can result in a cluster size of hundreds or thousands of blocks.

If you are using V7.2 and later, I suggest you check out HELP INIT/CLU and HELP INIT/MAX.

If you use a non-standard cluster factor, your BACKUP command will have to include the /NOINIT parameter on restore, or else BACKUP will initialize the disk.
http://www.stanq.com/charon-vax.html
P Muralidhar Kini
Honored Contributor

Re: VMS Image backup

Hi dudharkar,

Ya right. Similar suggestion from me.
If the disk in question is critical then its best to either setup volume
shadowing or have raid configuration, so that you have a backup disk in
case of disk failure.

In case of volume shadowing, you can pull out one disk for backup while
your applications continue to use the other disk for data.
Once the original disk is put back, volume shadowing would ensure that
both the disk would have updated data.

Regards,
Murali
Let There Be Rock - AC/DC

Re: VMS Image backup

If I use /log as qualifier after backup command then will it impact on time taken for backup.
P Muralidhar Kini
Honored Contributor

Re: VMS Image backup

Hi dudharkar,

>> If I use /log as qualifier after backup command then will it impact on
>> time taken for backup.

Yes. The "/LOG" qualifier determines whether the file specification of
each file processed is displayed to SYS$OUTPUT or not.
The default is "/NOLOG" in which case the file specifications for
each file processed is not displayed to SYS$OUPUT.

i.e. IF "/LOG" qualifier is used then for each file that is processed,
extra time would be taken to display file specification to SYS$OUTPUT.
It would take more time when compared to backup done with "/NOLOG" but
i dont think it would drastically bring down the time taken for the
backup as the data present in the disk itself is large (100GB).

In general image backup of a disk having 100GB worth of data is going
to take time.

Regards,
Murali
Let There Be Rock - AC/DC
Shriniketan Bhagwat
Trusted Contributor

Re: VMS Image backup

Hi,

Yes, /Log qualifier impacts the time taken by the BACKUP process.

To make your BACKUP faster, set the process quota values as described in the System Managerâ s Manual, Volume 1: Refer the section Setting Software Parameters for Efficient Backups. Link is provided below.
http://h71000.www7.hp.com/doc/82final/aa-pv5mj-tk/aa-pv5mj-tk.html

Also execute below command before performing the BACKUP.

$ SET RMS/BUFFER=127/ EXTEND=5000.

This command allows BACKUP to use more larger buffers when writing save set blocks to disk. The larger extend value reduces the impact of extending the save set file during a save operation.

Regards,
Ketan