Re: How to calculate storage space

raskew_at_axion.bt.co.uk (Ron Askew) writes:

>The answer to this question is probably RTFM, but can anyone tell me which FM
>contains the formulae to calculate the space required for tables and indexes.
 

>--
>Ron Askew, Internet : raskew_at_axion.bt.co.uk
>BT Labs, Telephone : (44) 473 643241
>Martlesham Heath, Fax : (44) 473 640279
>Ipswich, Suffolk, IP5 7RE

Chapter 8 of the Oracle7 Server Administrator's Guide contains information on how to size schema objects, such as tables, indexes, and clusters. Here you will find the implications of specifying PCTFREE and PCTUSED, the nuber of bytes for each datatype (e.g., a ROWID has a fixed size of six bytes for each row in the table), guidelines for estimating table size and storage parameters, and specific formulas for calculating table components. There is a good detailed description of the steps to calculate the initial extent size for a table:

1. Calculate the total block header size.
2. Calculate the available data space per data block.
3. Calculate the combined column lengths of the average row.
4. Calculate the average row size.
5. Calculate the average number of rows that can fit in a data block.
6. Calculate the number of blocks and bytes required for the table.

Chapter 7 of the Oracle7 Server Administrator's Guide has information on setting the size of tablespaces. I hope this helps.

Regards,
Bruce

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Bruce Gatterman                             Kendall Square Research
bruce_gatterman_at_ksr.com                     Phone:  1-617-895-9428
{harvard,uunet,world}!ksr!bruce_gatterman   Fax:    1-617-895-1632