on 02-16-2010 12:24 PM
Hi,
We have ECC 6.0 with Oracle on AIX 5.3.
I am taking backups onto tape using BRTools. The device file BRBackup recognizing is /dev/rmt0.1
First, I initialize the tape with the command:
brbackup -i force -v <tape volume name>
Then I will use BRTools to trigger backup.
My query is :
I have a set of 20 tapes loaded on to the cartridge. When all the 20 tapes are finished, I will have to take backup on to the 1st tape again. However, there will be a backup taken earlier on this tape.
How do I handle the tape that is already written once?
Do I need to initialize it again with a new volume name?
Is the new backup appended to the already taken backup or is it written from the beginning of the tape?
How do I restore the the current backup in case of a necessity?
Thanks for your help,
Abdul
How do I handle the tape that is already written once?
--> BRBACKUP will check expiry parameter in file initSID.sap. if it is passed that expiration, it will simply overwrite it. if not ,brbackup sill stop.
Do I need to initialize it again with a new volume name?
--> NO
Is the new backup appended to the already taken backup or is it written from the beginning of the tape?
--> NO
How do I restore the the current backup in case of a necessity?
--> You do that with BRRESTORE. go at http://service.sap.com/dbaora to get documentation.
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Dear Eric
Thanks for your quick response.
In my system, expir_period = 30 is set by default. I will change the value to 5 days to suit my backup cycle. However, at the time of restoration, will BRRESTORE recognize the tapes which are older than the expir_period? I am assuming a case where my recent backup tape volumes are faulty and I need to restore a volume which is quite old.
In my initSID.sap file, tape_address = /dev/rmt0.1 and tape_address_rew = /dev/rmt0 are set by default.
My BR*Tools is recognizing only rmt0.1 by default and writing to this device. So, my assumption is - new backups will be appended to the tape. Pls correct me if I am wrong.
One more thing:
When I search for tape devices on my aix system:
gspadm> lsdev -Cc tape
rmt0 Available 01-00-02 IBM 3580 Ultrium Tape Drive (FCP)
smc0 Available 01-00-02 IBM 3573 Tape Medium Changer (FCP)
Why is BRTools writing to rmt0.1 when there is no such drive?
Thanks in advance for your help.
Abdul
will BRRESTORE recognize the tapes which are older than the expir_period?
Yes, it will.
In my initSID.sap file, tape_address = /dev/rmt0.1 and tape_address_rew = /dev/rmt0 are set by default.
it should be more like this:
tape_address = /dev/rmt0.1
tape_address_rew = /dev/nmt0.1 (or similar)
Why is BRTools writing to rmt0.1 when there is no such drive?
check for soft links, check if fiel /dev/rmt0.1 maps to /dev/rmt0
On another note, you should read the following link to learn how to use SDN forums: http://www.sdn.sap.com/irj/sdn/crphelp
Dear Eric
Thanks for your response.
I have done a ls -l | grep rmt, and the result is:
crw-rw-rwT 1 root system 48, 0 Jan 24 12:51 rmt0
crw-rw-rwT 1 root system 48, 1 Jan 24 12:51 rmt0.1
Tape storage connected to my AIX system is IBM TS3100 model with only one drive. Is it the reason for not recognizing rmt0?
Secondly,
rmt0.1 is without rewind; if the expir_period does not occur, the new backup will be appended to the previous backup ? If yes, all my tapes in the library will finish in a few weeks. How do I manage the library in such a scenario? Do I need to change my initSID.sap file to reflect database backups to rmt0 instead of rmt0.1?
Thanks in advance for your help!!
Abdul
Edited by: Abdul Rahim Shaik on Feb 23, 2010 7:25 AM
Hi
tape_address=/dev/rmt0.1 and tape_address=/dev/rmt0 are pointing to the Tape Device Drivers to achieve two different functionalities/characteristics of that connected Tape Device/Drive in AIX system. Both are Operating System specifics.
Both are used for positioning and rewind operations while performing backup/restore operations using BR Programs.
Please refer [this useful link|http://blog.worldiswelcome.com/science-and-technology/aix/backups/2009/03/all-you-wanted-to-know-about-aix-tape-device-backups-ii/] to get more information.
with /dev/rmt0 (rewind driver)
The backup/restore operation will start at the point where the device pointer is at present.But, the tape is rewinded to Zero position once the backup/restore operation is finished.
with /dev/rmt0.1 (no-rewind driver)
The backup/restore operation will start from the previous point where the pointer was, at the end of previous backup/restore operation. Similarly, the tape is not rewinded to start after the backup/restore operation is finished.This is the most common option used in tape backups.
As per this [SAP Note 4160 - Tape management for recovery|https://service.sap.com/sap/support/notes/4160],
When using the "rewind driver" , the tape is automatically rewound to the beginning after completion of the command.
Positioning (e.g. mt -f/dev/rmt/0mnfsf <#>) sets the tape to the<#+1> file. E.g.:
mt-f /dev/rmt/0mnfsf 4 positions to the 5th file.
The "rewind driver" must used for rewind, the "norewind driver" for positioning.
Use the"norewind driver" for restore and file displaying, so that the tape head is then always automatically set to the next cpio block.
The value of expire_period is the retention period for the Tapes writen by BRBACKUP/BRARCHIVE. If you have set expire_period=5 then, on 6th day the Tape will be overwritten. It means that writing to a volume is possible 5 days after the volume was mounted and used.
Please do not change the existing settings of tape_address and tape_Address_rew parameters.
By keeping in mind the following factors,You can design your Backup Cycle Strategy.
The Role of System in Business, the Size of Database, The size of Tape, Growth Rate of Database, Number of Backups per Backup Cycle, Frequency of Backup operations, The data protection period, etc.
Regards,
Bhavik G. Shroff
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