DB Page Size 4K --> 16K Increment for a Unicode Migration?

[former_member229542]

Hi Guys

Currently we are migrating a SAP system 47x200 Non-Unicode which has a page size 4K due installed DB2 version is 8.1

Since the target Database is v 9.7 and also we are performing an Unicode Migration, i´d like if you can shed some light on recommended Page Size

I understand latest SAP Installations has a 16k page size as default, and also for UNICODE systems to acommodate the increased row width.

Therefore I would assume is mandatory and/or recommended to convert page size from 4k to 16k?

Is there any SAP Note with this recommendation, so I can forware it and discuss this with DB Team.

Thanks!

[Frank-Martin · Accepted solution]

Hi Martin,

this should be a no-brainer for you.

A unicode migration is not done inplace in the existing database. Basically it is an export/import of your data using SAP tools. SAPINST/R3load will be used to export your data from your non-unicode system. On the other end you will create a new unicode database using SAPINST. After that SAPINST will import the exported data into the new database using R3load. In this process R3load will perform the codepage conversion. SAPINST will automatically create the new unicode database with uniform 16K pagesize for you independent of the database pagesize of your current non-unicode database.

Regards

                  Frank

[former_member229542 · Accepted solution]

Hi Frank

Thanks for this valuable information.

Regarding Import/Export Process I have a few question?

Can be estimated the size of the export file which is created? Since we have to setup an additional filesystem to accomodate this process.

Also, 4k/8k TS which are dropped and replaced by newer 16k TS, are created on the same containers as the original filesystem layout?

Thanks again!

[Former Member · Accepted solution]

Hi Martin,

Ruke of thumb for setting of export file is one tenth of the database size + 10 GB over heads.

For example if your DB size id 500 GB you can set an export file system ( 500 GB / 100 ) = 50 GB + 10 GB overheads. That means 60 GB. For bigger database more than 1 TB keep the overhead part atleast 20 GB,

Regards,

Dipam

[Former Member]

Hi Martin,

For ECC system I would like suggest only 16K page size. I did couple of Unicode migration as well as OSDB migration for DB2 UDB LUW - and I always set pagesize as 16 K. There are three things you need to sync

-- Page size of database ( 16 K)

-- Page size of bufferpool ( 16 K)

-- Page size of tablespaces.

That means with database of 16 K page , create custom buffer pool of 16 K and all SAP tablespaces assigned to 16 K bufferpool.

As per the best practice you should not go for bigger buffer pool like 32 K  - result in wasting storage space due to large fragmentation. On the otherhand you should not go for smaller page size like 4K - due to performance issue - due to smaller page size DB process needs read more pages to access smaller amount of data.

It is common in BW system you can configure with different bufferpool size and taablespaces.

Regards,

Dipam