topic Re: db_block_size and operating system block_size parameter in Operating System - HP-UX

db_block_size and operating system block_size parameter

Jose Luis De Diego — Tue, 08 Jan 2002 10:49:06 GMT

Hi all.

Does anybody know how to find out the OS block_size on vxfs in HPUX 11?

I'm trying to adjust SGA, and one of the parameters involved is, as you all know, db_block_size, which must be multiple of the OS block_size.

I know you define it when creating the file system, but I don't remember the value, and don't know where nor how to visualize the value.

Thanks in advance.

Re: db_block_size and operating system block_size parameter

John Palmer — Tue, 08 Jan 2002 10:55:41 GMT

fstyp -v /dev/vg??/???

will return the blocksize as f_bsize and the fragment size as f_frsize.

Regards,
Joh

Re: db_block_size and operating system block_size parameter

Duncan Edmonstone — Tue, 08 Jan 2002 10:58:56 GMT

Two ways:

fstyp -v /dev/vgXX/lvolY

And look at the value given for f_frsize

OR

mkfs -m /dev/vgXX/lvolY

which shows you the original mkfs command used to create the file system.

Unless it was specified at creation time, VxFS file systems will default to a block size of 1024 - this is probably a bit small for most Oracle databases - most people seem happy with a block size of 8192.

HTH

Duncan

Re: db_block_size and operating system block_size parameter

Jose Luis De Diego — Tue, 08 Jan 2002 11:58:15 GMT

I understand the parameter Oracle recommends to be a multiple of the FS block_size, *for vxfs*, is f_frsize or fragment size, which is the same as specified when creating the FS with mkfs and bsize option.

Thanks, Duncan and John.

Greetings.

Re: db_block_size and operating system block_size parameter

Darrell Allen — Tue, 08 Jan 2002 15:35:00 GMT

Hi Jose,

There is much confusion on this issue. Here's a doc:
http://us-support3.external.hp.com/cki/bin/doc.pl/sid=c4b25c3a08f59ac82a/screen=ckiDisplayDocument?docId=200000054230626

Also, from man newfs_vxfs:
-b block_size File system block size in bytes. The default value used is 1024 bytes.

Look for f_frsize from:
fstyp -v /dev/vg##/lvol#

Look for fragment size from:
df -g /mount_point

There's quite a number of threads in the forums about this. I suggest you search (limiting the domain to itrc.hp.com) at http://www.google.com/advanced_search

Darrell

Re: db_block_size and operating system block_size parameter

Jose Luis De Diego — Wed, 09 Jan 2002 10:49:36 GMT

Darrell.

The info you gave through man pages and other commands have been enough for me to solve my doubts, specially man newfs_vxfs, man df, and man statvfs, which is the C system funtion for retrieving file system info, and that is called from command line interfaces like df, and so on.

Here is an extract of man statvfs, which I think make clear the issue:

man statvfs
Reformatting entry. Wait... done

statvfs(2) statvfs(2)

NAME
statvfs, fstatvfs - get file system information. These C funtions are called from command line interfaces, like df.

DESCRIPTION
statvfs() returns information about a mounted file system.
...

The statvfs structure contains the following members:

...
ulong f_frsize; /* fundamental file system block size */
...

Of course John and Duncan gave the right answer as well...

;^)

Greetings.