Re: Migrate from AIX to Linux

  • From: William Sescu <william.sescu@xxxxxxxxx>
  • To: dmarc-noreply@xxxxxxxxxxxxx
  • Date: Fri, 18 Dec 2015 11:16:33 +0100

In case you use a more recent version of Veritas on Linux (e.g. 6.2.x), you
can use the CIO option as well.

# man mount_vxfs
...
...
cio Mounts the file system for concurrent reads and
writes. Concurrent I/O (CIO) offers performance benefits
for well-behaved major commercial databases via
mechanisms of unlocking and unbuffering. Only these
databases and other applications that do not need
POSIX concurrency guarantees should use CIO.

The cio option cannot be disabled by remounting
the file system. To disable the cio option, unmount the
file system, then mount the file system without the
cio option.

Cheers,
William


On Thu, Dec 17, 2015 at 9:34 PM, Deepak Sharma <dmarc-noreply@xxxxxxxxxxxxx>
wrote:

We are still ways out before we implement the solution (several months),
but will definitely keep posted.

I had a kind of related question w.r.t. AIX vs Redhat Linux. Currently we
use CIO with AIX. Is there anything equivalent on Linux (that doesn't
involve ASM)?


On Thursday, December 17, 2015 12:48 PM, Andrew Kerber <
andrew.kerber@xxxxxxxxx> wrote:


I am interested to hear how it goes, and how many rehearsals you plan
before the final go live.

-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Mladen Gogala
Sent: Thursday, December 17, 2015 12:17 PM
To: Deepak Sharma; oracle.blog3@xxxxxxxxx
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: Migrate from AIX to Linux

On 12/17/2015 12:52 PM, Deepak Sharma wrote:
Now, since you have experience with actually doing the migration, let
me know if this would work (we will of course try it out soon too):

1. Copy the 'datafile copies' from source to destination staging area
This can be achieved with a minimal downtime, by shutting down the
database and snapping LUNs which contain the database. That is equivalent
to a cold backup, only two orders of magnitude faster. After the snapshot,
the database can be restarted.


2. Run the 'convert from platform' RMAN command, to convert those
datafile copies so they land in the real datafile locations

Mount the snapshot onto the target machines and run "rman convert" to real
locations. Re-create the control file with the new file locations.
Since the target is Linux RAC, those will most probably look like this:
'+DATA/<db_unique_name>/datafiles/......'. Something like "vi" with
global string replace capability would be ideal for editing "create
controlfile" statement.

3. Copy the subsequent 'Incrementals' from source to destination area

Everything else remains the same. And yes, I have done that.

4. Convert the Incrementals on destination to apply to real datafile
(from Step 2).
5. Repeat 3 & 4, until you're almost caught up, and do a final 3 & 4
with source tablespaces being read-only.

Does this make sense? Pls share your thoughts.
Yes it does. However, few steps have been left out. I am not sure whether
AIX db is single instance or RAC, but you will need to add the undo
tablespace for each instance and create as many redo threads as you have
instances. Single-instance database has only a single active redo thread.
You will also need to add instances to OCR by using srvctl add instance.
Only when that is done, you will have a full fledged RAC database on Linux.

Also, be very careful when performing loads. Make sure that the same
tables are only loaded from one machine. Good luck, may the force be with
you.
Regards


-thanks



--
Mladen Gogala
Oracle DBA
http://mgogala.freehostia.com


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