Rgdg the Tape Drive Device file

[Dinesh_15]

Hi All

I am regularly visiting the ITRC and it helps me to make myself technically sound.recently I have seen queries rgdg the Tape Device files and after reading I thought of posting my queries above that. But posting as a sepatare seems better and here is my doubt. hope somebosy will clear.

1)In case of 0mn devices after taking backup the media is not rewinded.So if while recovering whether system automatically rewinds the media. I think this is must as the media headers are writtem in the begining.

2) In case of Ignite backup after rwinding, fast forwarding and then recovering a single file / directory,how the media will refer the end of the data as we r using 0mn for creating the boot archive.

3) In case of tar whether there will be any difference while using 0mn and 0m device files

Rgds
Dinu

[Devender Khatana · Accepted solution]

Hello Dinesh,
1. This is a fact that after backup if you specify 0mn it will rewind media after backup. But whenever we eject and reinsert media Or recycle power to drive it is rewinded.

2. In fast forwarding once it will not go to the end of media but actually will go to the 2nd mark of the Media where data is written in same or different format. ( This means you can use your one media for multiple backups) For achiving this take first backup without rewind option (Omn) and when it finishes take another backup with or without rewind option. Now two sessions are stored in your media. If you have taken backup without rewind option you can take another backup & it will become your third backup on single media.

For accessing 2nd backuop session on single media :-

a) Either Recycle power to drive or reinsert media or execute
$mt -t /dev/rmt/0mn rew

b)For going to 2nd session
mt -t /dev/rmt/0mn fsf 1

For going to 2nd session
mt -t /dev/rmt/0mn fsf 2

c)After going to the particular session you can execute particular command to extract data. ( The command in which archive was created)
You can have multiple different format sessions on single media & same is the case of out IGNITE tape, The header is in LIF format & 2nd session is in tar format which contains data.
3. The relevance of 0m & 0mn is same for all backup commands.

HTH,
Devender

[Dinesh_15]

Hi Devender

Thanks a lot for nice explanation.

I am closing the thread

Rgds
Dinu