NUSI space utilization


NUSI space utilization

How can we know the space used by an NUSI?

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Re: NUSI space utilization

In 13.10 Database Design documentation it is the section 'NUSI Sizing Equation' and 'NUSI Space Considerations' in 'Chapter 15: Database-Level Capacity Planning Considerations Sizing a Nonunique Secondary Index Subtable'

I usually use a bruce force approach. Not very sophisticated...

1. Create a 1:1 copy of the table.

2. Insert select some data with sample like insert into copy_sample select * from source sample 10000000. The sample size depend a bit on your system size. In small configurations might be 1 mio sufficient.

3. Measure copy_table table space

4. drop nusi

5. Measure copy_table table space again

6. calculate NSUI space as % of diff

7. calculate source table space and weight with the % of step 6 -> approx. NUSI space.