backup with DLTIV on TZ88 fails

[Michael Schulte zur Sur]

Hi,

I have the problem that the vdump seems to be ok but the vrestore -tv aborts on different tapes roughly at the same location.
Are there any known compatibility problems?
According to man tape the TZ88 should be able to handle DLTIV.

thanks for any insight,

Michael

[Mohamed K Ahmed]

Michael,

What are you trying to do exactly?
What is the size of the data ?

If the backups run ok, then reading from the tape while restoring should be OK.
You are using vrestore -tv , are you just trying to see files on the save set or want to restore them?

Mohamed

[Michael Schulte zur Sur]

Mohamed,

thanks for your answer. I just want to check the quality of the backup after vdump not to restore it. At the moment it is starting to look like that the tapes are losing their capacity. I tried with a new and that worked. We will exchange the rest too. I wonder however that the write did not fail.

thanks,

Michael

[Mohamed K Ahmed]

Well, I have noticed that during my backup schedule. I backup systems with Oracle databases, some of the drives have just flat data, the others hav Oracle tables and data.
It seems that the compression through the tape drive or through the system command is better when backing up oracle files. I can backup 100GB of oracle data file to a DLTIV, while I can just backup about 60GB of flat files onto the same tape.

[Michael Schulte zur Sur]

With capacity I meant the tape to receive new information.

Michael

[Uwe Zessin]

An 'empty' database can be better compressed if it fills the data files with a fixed bit pattern (I think Oracle does this). When you start writing real data to your database it begins to require more and more space on tape, because the user data cannot be that good compressed like a constant bit pattern.

Another reason for loosing space is when the tape quality goes down when the tape drive starts to re-write blocks.

But it is strange that you can write to the tape media, but apparently cannot fully read it. Is there anything helpful in the error log?

[Michael Schulte zur Sur]

Uwe,

I find it funny that Oracle sneeked in here because it never was an issue. The main question is that the write does not cause an error but the read. I will have a look into the binary errorlog for errors.

Nice performace! If I don't pay attention you will pass me on my way to the dunes.

thanks,

Michael

[Uwe Zessin]

Yes, I understand - sorry for hijacking your thread to discuss Oracle...

And thank you for the compliments. Have no fear - you're way ahead of me.

[Alexey Borchev]

Michael,
Are You trying to read tape by another streamer?
Can You read it with the original streamer?

If the TZ88 also known as SDLT (or Super DLT?)
I've got an experience with SDLT 320 (native 160, compressed 320GB) - it is capable of reading DLT IV (35 / 70 GB) tapes. It does working.

You can try vdump -x option (XOR checksm block, kind of RAID5 technology).

If there anything in binary.errlog?

There is tape exerciser /usr/field/tapex
- Your can try the tool to write & verify data. There tool has the "transportability" test - write on one streames, read on another.
Takes ages to fill up the whole tape :-(.

[Uwe Zessin]

The TZ88 is a 'plain' DLT tape drive that can store 20 GigaBytes uncompressed max. and works with DLT IV, CompaqTape III, DLT III-XT media.