Migration from Oracle to DB2

[former_member248069]

SAP and IBM approached us lately to convert our databases from Oracle to DB2 in order to save on storage cost because of DB2 deep compression feature. Oracle 11g has advanced compression feature which is equivalent to DB2. However, SAP is not yet supporting Oracle 11g and there is no word on when.

I wonder if anyone out there has experienced the same? (migrating from Oracle to DB2) ? What are to pluses and minuses to consider? Remember, its is strictly from an cost saving argument. Oracle is working well for us. IBM claim to reduce storage usage by 30% ~ 40%. Our largest database id approaching 6TB.

Thank you for your help.

[Former Member]

Hi Duc,

please read this link I posted wich has some good white papers discussing the topic:

bye

yk

[stefan_koehler]

Hello Duc,

at first you can read this paper that was published by the IBM to get a better understanding of the compression feature and how it works in a SAP system: ftp://ftp.software.ibm.com/software/data/pubs/papers/DB2-SAP-compression.pdf

> Oracle 11g has advanced compression feature which is equivalent to DB2

That is what IBM tries to tell you but if you see behind the curtain, you will see the whole truth. Afaik DB2 is not performing a "Live-Compression" of new value combinations. You have to maintain this dictionary that is used for the compression from time to time.

SAP supports "index key compression" with Oracle 10gR2 and the table compression will be supported with Oracle 11g. But keep in mind that Oracle does a "Live-Compression". If i am wrong with the DB2 part please correct me, but that's the way that was told to me by a DB2 admin that i met some time ago.

> SAP is not yet supporting Oracle 11g and there is no word on when.

You are correct that there is no timeline, but it will be supported with Oracle 11g R2 (so it mostly depends on Oracle).

If it is all about saving disk space i wouldn't do it, but mostly IBM is also much cheaper with the licenses.

Regards

Stefan

[brian_walker]

Duc,

Which flavor of DB2 (LUW or z/OS) and which platform (Windows, AIX, Linux, z/OS, etc)? My experience is that DB2 compression does achieve the stated range of 30% to 40% reduction in storage. I also believe that DB2 z/OS is the only DB2 platform where the compression is hardware based. I am not sure about DB2 LUW, but for DB2 z/OS the compression will not be available during installation and will only be taken advantage of after a reorg of each tablespace where compression is desired (SAP note 1062976 indicates SAP is working on the compression being enabled during an installation).

I think the answer to your question depends on which Oracle platform you are on now, which DB2 platform you would implement, what the cost of disk space is on both, and what kind of experience you have at your company with DB2. If you have very little DB2 experience, then any cost reduction in disk space utilization could easily be taken up by having to learn another database platform. While the concepts are similar, the way backups, statistics, reorgs, etc. are peformed are totally different.

From experience, I would be extremely wary of any vendor trying to get you to change platforms for a cost reduction. Personally, I think I'd wait for SAP to support Oracle 11g. If you do migrate, you'll have to use the database agnostic SAP system copy procedure and that usually means a rather lengthy downtime to export the current database and the re-install on the new database. Of course the downtime will be dependent on the size of the database.

Brian

[former_member248069]

Thank you for the quick response. I forgot to mention we are running on AIX 5.3 and the proposed database is DB2 UDB 9. I understand we'll need to do a system copy and IBM is proposing doing the Unicode conversion, which is a clever move.

We're working on our own on Unicode conversion for the ECC 6.0. There is no words from SAP when Oracle 11g advanced compression will be availabe. Does anyone have any more info?

[Former Member]

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[Former Member]

Hi,

hope it's not already decided to move to DB2.

11g does the new "Advanced compression" in the background intoducing a new Oracle process (keeps system resources to a minimum).

fwhite papers for the feature

http://www.oracle.com/technology/products/database/compression/index.html

Statement for supporting Oracle 11.2:

http://www.oracle.com/newsletters/sap/products/database/relstrat.html

"SAP AG will skip Oracle Database 11g Release 1 and certify Oracle Database 11g Release 2, at least 12 months before Oracle Database Release 10g goes into the extended support cycle. Oracle Database 11g Release 2 will contain various specific functionality designed and implemented for the needs of the SAP Application Product Suite"

So you may not hesitate to move so quickly...

on 9i / 10g you have some constraints with compress/uncompress but it depends on your acces pattern of the tables (more kind of static tables w/o many DML on it).

We use it on SAP BW 3.5 and could reduce the storage needs around 65- 75% of the original table size.

So our 100 Gbyte table only had 35 Gbytes after compression.

Can give you a good link to a PPT document for SIG SAP / ORACLE 20080609-SIG_SAP-Berghof-Compression.pdf

Think of it:

• you are not bound to ANY hardware (oh yes you got DB2 deep compression, but , sorry, you need the IBM hardware stuff also)

• you can administer compression with SQL commands (no "outside" tools needed)

• it doesn't constrin your physical and logical DB layout

• and ... it also reduces storage costs (that was the main reason why they introduced it for large DW)

• last but not least: compressing is a cool thing BUT could not be the only criteria to do a move into another product. There are way of other features where Oracle leads

That SAP (claiming to be database independent forces you to DB2 is a marketing strategy ...at least hope they pay the migration to the new DB and the education of the DB Admin staff for DB2

(rol)

bye

yk