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number of datafiles to add

Dear Gentlemans,

Do you know a sapnote or any source which recommends to add 2 or more data files (because of data load distribution)?

I think adding only one data file when it is needed is not harmful and keeps costs low.

for example: we have 33 data files with 20Gb size, but we add only one 20Gb when we reach 80% fill level.

The version is MAX DB 7.6.04.15

Thanks in advance!

Tibor Meszaros

Former Member
replied

Hi Tibor,

the answers to questions like these could usually be found in notes like '1173395 - FAQ: MaxDB Konfiguration'.

Concerning the question about rather adding one data volume everyime or more it's quite difficult to give a general optimal answer.

When you add the new volume when the data area is used up to 80% than all subsequent changed pages will be written to this new volume until the the usage is evened out over all data volumes (e.g. the usage for all volumes has dropped to 75%).

Since the writing is done asychronously this is usually not an issue.

Anyhow, in extreme cases (e.g. huge amount of changed and added data + very small cache + rest of the volumes filled up 100%) adding more volumes than one at a time might turn out beneficical.

As a general guideline you simple should take care to keep the freespace on a level where you know that you've enough time to add a new volume until the increase of data leads to a DB FULL.

hope that helps,

regards,

Lars

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