Oracle and different PE size on two server

[Mauro Gatti]

Hi all, I have two server with hpux 10.20
On server A I have volume groups created with PE Size of 4 Mb.
On server B I have volume groups created with PE size of 8 Mb.

On these VGs there are some oracle datafiles.

Server A is "production" server and server B is "test" server.

I do a "cold" backup of these datafile on server A to tape (so I stop oracle and then I start backup) and next I restore them from tape to server B.

Unluckly my DBA tell me there are incongruencies on "blocks" on datafile on server B.

Do You think this can be caused by different VG PE size?

To change PE size I think I have to destory and recreate VG, isnt't it?


Thank You for your help


Mauro

[Robert-Jan Goossens]

Hi Mauro,

No this should make a difference,

could you check next command on both filesystems (servers)

# df -g /oracle_filesystem

Robert-Jan

[Jean-Luc Oudart]

PE size has nothing to do with Oracle blocks and so on.
This is just an allocation unit.

Jean-Luc

[Tomek Gryszkiewicz]

PE size doesn't matter in this case. PE only matters when you extending or creating lvols.

-Tomek

[Julio Yamawaki]

Hi,

When your DBA told about "incongruencies on blocks", you must check the blocksize of the two databases and check the blocksize of the filesystems where this database is housed.
In Oracle: check parameter db_block_size
In Unix: fstyp -v /dev/vg/lvol, check fr_size

[Jean-Luc Oudart]

Could you get the exact Oracle error message from the DBA ?
This should be in the alert logfile

Regards,
Jean-Luc

[Mauro Gatti]

db_block_size is 8192 and f_frsize is 1024 on both server.

I can't be able now to tell you the exact error code of oracle.
I know only oracle found an inconsistency from "actual" (on server B) file dimension and "expected" dimension.

Thank You again.

[Hein van den Heuvel]

Well, just don't take no for an answer and work with the DBA to get clear error messages. You may alway want to check and compare the actual file sizes... why not.

If you know for a fact that all data for all db files has been transferred correctly, then you may just want to activate the cloned database using 'CREATE CONTROL FILE' passing in the list of (new) file names.

You get the template for the create control file by doing a 'backup controlfile (to trace)' on the production box.
Btw... it is always prudent to have such control file script handy to recover from massive problem (operator deleting control files :-).


Hein.

[Steven E. Protter]

Yes, to change the PE size you'd want to back up the data with fbackup or something, destory the volume group and recreate it with the right
-s parameter.

As far as this bothering Oracle, I'm kind of wondering what the word inconguencies means.

There might be a performance impact.

I posted a thread a while back asking if I could boost Oracle performance by useing larger PE size and A. Clay Stephenson, I believe told me that from experience it would not make a difference.

I only vary from default pe-size when I need to have a large mount if data in a single volume group and was running into OS limitations on number of pe units(-p )usable in a volume group.

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