Writing to tape from C system calls

["Ujval Lodha" <ujval@gdc-tech.com>]

Hi

I'm new to tape devices.

My application requires me to seek to a certain block on the tape device and
write data on it (besides being able to retrieve data by reading).

So far, I have no trouble reading from the tape.

When I write to it at any block that block becomes the last block on the
device. I am unable to seek to any block after that on the tape. I have
tried :

    a. Using mt to seek and dd to write
    b. Using open / ioctl / write from C

Both with the same results. I am using a Tandberg SDLT for my tests with the
linux kernel st drivers.

Is this normal? Is it not possible to use the tape device - and modify data
at any block by seeking to it and writing?

Is there some source of information where I can read about programming tape
devices from C? So far, I havent been able to find one.

Please advise.
Regards,
Ujval Lodha