Migrate from DB2 to Oracle

[Former Member]

Hi Experts,

I have inquiry regarding down time when doing db2 migration from DB2 to Oracle. How long do we need to spend down time. If you have any experience or information regarding this, please let us know.

Thanks & Regards,

Rudi

[markus_doehr2]

Nobody will be able to answer that question.

It depends:

- of the speed of the I/O subsystem

- the number of parallel R3load processes you use

- the number of processors in both source and target system

- splitting of the tables or no splitting - and how

You can check what I wrote in thread

to get an avg. overview of how this can be done.

As already said, you need to have a certified migration consultant on-site to do the migration, otherwise you will loose support for the target system.

Check http://service.sap.com/osdbmigration

--> FAQ

Markus

[Former Member]

Hi Markus,

Is it possible to calculate roughly? e.g. can we know the number of days of downtime by only knowing db size? Because we only have maximum 4 days for downtime, including fallback plan.

On your opinion, which easier and which has low risk, between migrate db and upgrade db?

Thanks in advance.

Regards,

Rudi

[markus_doehr2]

Speeding up the export and import is an iterative process, you will start with a certain configuration and need to check if the speed is sufficient (which is most likely not the case), then check which tables are taking the most long and split them.

The only way to find that out is to do the migration once to see how long you need.

Markus

[Former Member]

Hi Rudi,

assuming that your current environment is not to bad (it runs, at least a 3TB system), then I would expect much less downtime possible then four days. I did a Unicode migration of a 3TB ECC6 System within 24 hours (in the opposite direction Oracle -> DB2). There is a report UMG_R3LOAD_RUNTIME_PREDICTION which is usually used for runtime prediction of Unicode migrations. You may use it also for an estimation for your migration. Unicode migrations are usually slower than normal migrations, but with the report you may get a feeling for the time necessary. You may download the report ZUMG_R3LOAD_RUNTIME_PREDICTION which is attached to note 857081, when you know all necessary input.

There are also some rules of thumb out there to estimate runtimes:

Export/Import Time:

3.6GB/h per 1GHz CPU Ticks ==> for 8 Core 2.8 GHz Server: 3000GB / (8 * 2.8 * 3.6 GB/h) = 37,2h

Export/Import Time:

13.5GB/h per 1000SAPS ==> for 10000 SAP Server: 3000GB / (10 * 13.5GB/h) = 22h

But you also have to take into your calculation your disks (with Interfaces) and NICs. E.g. one 2Gbit FC HBA could transfer up to 700GB/h, therefore you need >40 Disks per HBA to achieve 700GB/h But this should not be your problem (I assume). After all you need to transfer the dump in time. When you use application servers for export you'll transfer all data uncompressed within time. One 1Gbit NIC could transfer something about 350GB/h. If you run a central system (what I don't expect) then you transfer only 10% of your database size over network (just the dump).

All these numbers above could be reached if you do all things wright. You can easily need ten times more when you do it wrong. You should ask an experienced consultant to help you for such a project, if you ask me.

Regards

Ralph

[Former Member]

Hi Ralph,

Thanks for the advice.

Regards,

Rudi

[Former Member]

This activity must be performed by DB certified consultants from SAP. ot i think SAP will not support in case of any issues

[Former Member]

Hi Rudi,

Question asked by you is very difficult to answer for any technical guy.

Its all depend on the database size and hardware you are using for the migration you can not predict downtime for your mnigration based on the other migration.

Suggestion would be perform the test migtation first on your system so that you will get an idea how much downtime you will need for your sysyem when you will pefrom actual migration.

let me know if you have any other questions.

Regards, AG

[Former Member]

Hi Atil,

I read from oracle official docs, they said that they can predict the downtime. Our db size is about 3TB using AIX 5.3 on P5 machine.

Regards,

Rudi