Not used real tapes in years but back in the dark ages I would increase the block size until the 'write' light on the tape unit was continuously on, not very scientific but seemed to work
Cheers
Paul
On 12/22/2022 7:57 AM, Andreas Legner via IBM Community wrote:
010001853a1f8850-ed76e595-561f-475c-87bf-4b2dd15ec439-000000@email.amazonses.com"> Shouldn't this be a property of your tape device, i.e. come from your Ultrium documentation? ------------------------------ Andreas Legner ------...
Original Message:
Sent: 12/22/2022 8:57:00 AM
From: Andreas Legner
Subject: RE: Ontape parameters
Shouldn't this be a property of your tape device, i.e. come from your Ultrium documentation?
------------------------------
Andreas Legner
------------------------------
Original Message:
Sent: Wed December 21, 2022 08:48 PM
From: Gustavo Echenique
Subject: Ontape parameters
Excellent explanation Art!
With this way of graphing, the work of the recorder heads is perfectly understood.
What TAPEBLK would you recommend?
Thank you very much again!
------------------------------
Gustavo Echenique
Original Message:
Sent: Wed December 21, 2022 06:08 PM
From: Art Kagel
Subject: Ontape parameters
Gustavo:
So here is the deal with backing up to tape and block sizing. The following is very simplified! Experts be kind!
Tape backup systems are also called "streaming tape" backup systems. When you begin writing to a streaming tape, the drive starts running tape past the write head. Ontape begins by writing a header block that is the "TAPEBLK" size. Then it waits until the tape device acknowledges the write was successful before writing the next block. Meanwhile the tape is still streaming past the write head with nothing being written so there is a gap. Those gaps are all the same size (with a few exceptions I suppose). The smaller the write block the more space on the tape is wasted in the inter-block gaps in the data written to the tape. If you could "see" the data on the tape, small block data looks something like this:
XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX
Double the block size and it looks like this:
XXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXX
In the second set we got 120 X's in less space than the first set stored the same amount of data.
On disk, if you write an archive to disk, there is no wasted space, so block size really does not matter. But on tape, it does.
Art
------------------------------
Art S. Kagel, President and Principal Consultant
ASK Database Management Corp.
www.askdbmgt.comOriginal Message:
Sent: Wed December 21, 2022 05:49 PM
From: Gustavo Echenique
Subject: Ontape parameters
Dear colleagues:
I need to make backups on tape.
I have an external HP LTO Ultrium 6 drive with native 2.50TB cartridges, and my problem is focused on the TAPEBLK parameter, which I had at 2048 when I backed up to disk, but when I want to do it to tape, the ontape tells me that does not support that block size.
I tried 1024 and it worked, but I'm wondering since Tivoli Storage Manager recommends a block size no greater than 256.
I would like someone to explain this topic a little more in detail.
Thank you in advance for your attention.
Gustavo Echenique
------------------------------
Gustavo Echenique
------------------------------
#Informix