Horacio
Here is an excerpt from our tech notes database:
DB2 And Block Sizes
There is a restriction on the number of FIXED block sizes that can be used
due to the fact that DB2 writes out the backup image header as a 4K block.
The only fixed block sizes that we support are 512, 1024, 2048 and 4096
bytes. If a customer is using a fixed block size, they can specify any
buffer size for the backup. My experience with backup on AIX and fixed
block sizes has been that the backup will NOT complete successfully if the
fixed block size is NOT one of the ones above (result - sql2025; return
code "2") but this may not be true in general.
Unfortunately, it will take some customers forever to backup large
databases with such small block sizes. In this situation, some customers
specify a VARIABLE block size (set to 0 in AIX for example). The backup
command will succeed if the block size is set to variable, however a
customer may not be able to restore from that backup image (result -
sql1025; return code 2)! This is where the buffer size parameter of backup
comes into play. Customers using a variable block size MUST also specify a
buffer size in the backup command that is <= the maximum block size limit
for the tape device they are using. For maximum performance they should
specify a buffer size = the max block size limit of the device. Some
examples are below but the customer should double check their device's
limit themselves.
Device Attachment Block Size Limit DB2 Buffer Size Limit (in 4K pages)
8mm scsi 131072 32
3420 s370 65536 16
3480 s370 65536 16
3490 s370 65536 16
3490E s370 65536 16
3490 s390 65536 16
3490E s390 65536 16
7332(4mm)* scsi 262144 64
3490e scsi 262144 64
3590** scsi 2097152 512
3570 262144 64
(magstar MP)
(*) The 7332 does not implement a block size limit. 256k is simply
a suggested value. Block size limit is imposed by parent adapter.
(**) While the 3590 does support a 2MB block size, you might
experiment with lower values (256k) provided performance is adequate.
_____________________________________________
Dale M. McInnis IBM Toronto Lab
Senior Technical Manager, DB2 UDB Backup, Data Protection and Recovery
Email: [EMAIL PROTECTED]
Phone: (905) 413-2397, Fax: (905) 413-4685, T/L: 969-2397
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| | Villa Horacio |
| | <[EMAIL PROTECTED]> |
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| | a.best.com |
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| | 08/28/2001 03:59 PM |
| | Please respond to |
| | db2eug |
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| Subject: RE: DB2EUG: I/O error "2" on backup
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Dale,
tapeutil -f /dev/rmt0 parms lists the following:
SCSI max Xfer = 2097152
this value is 512 * 4K.
The tape block size, as defined in AIX is 0, being max block size 16777215.
Is this SCSI max Xfer a limit I can't override?
Regards,
Horacio Villa
-----Mensaje original-----
De: [EMAIL PROTECTED] En nombre de [EMAIL PROTECTED]
Enviado el: Lunes 27 de Agosto de 2001 15:05
Para: [EMAIL PROTECTED]
Asunto: Re: DB2EUG: I/O error "2" on backup
What is the tape block size, as defined in AIX?
_____________________________________________
Dale M. McInnis IBM Toronto Lab
Senior Technical Manager, DB2 UDB Backup, Data Protection and Recovery
Email: [EMAIL PROTECTED]
Phone: (905) 413-2397, Fax: (905) 413-4685, T/L: 969-2397
Villa Horacio
<[EMAIL PROTECTED]> To:
[EMAIL PROTECTED]
Sent by: cc:
[EMAIL PROTECTED] Subject: DB2EUG: I/O
error "2" on backup
a.best.com
08/27/2001 12:19 PM
Please respond to
db2eug
Hi,
I sent the message with this subject last wednesday and got no reply.
Since then, I tried many alternatives till I discovered the problem is
related with
buffer 1024.
If I change buffer 1024 to buffer 512 if works.
Is this the maximum I can specify or is it related to the database manager
configuration parameter backbufsz?
I'm running DB2 7.2 on AIX 4.3.3, the tape device is LTO something.
Kind regards,
Horacio
Hi everybody,
I'm getting SQL2025N during a backup command to /dev/rmt0.
backup database digital tablespace (tbsp1, tbsp2) online to /dev/rmt0 with
2
buffers buffer 1024
I position the tape with tapeutil and think it's correct.
What is I/O error "2" or where can I find it?
TIA
Horacio Villa
TTI S.A.
Buenos Aires - Argentina
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