Rollback segs #/sizes?

Hi;

I tried posting this message to comp.databases.oracle.server about a week ago and got absolutely no responses, so I thought I'd try here.

I'm reading through the Oracle 8i DBA Handbook and have finally hit the chapter on rollback segments. The book has a fairly involved process for identifying the correct number and sizes for the rollback segments. If I understand the process, it's as follows:

1. ID the rollback segment entry volume
2. ID the number of transactions
3. Calculate:
4. Min possible size for each segment
5. Min combined size for all segments
6. Min number of rollback segments
7. Max number of rollback segments
8. ID appropriate balancing act, if necessary, between large number of small transactions and small number of large transactions.

That little checklist covered about 15 pages of the book. Is this the way it's really done in the field? I've been a UNIX admin for about 12 years now, most of which has been supporting Oracle admins. I have a hard time believing that the people I've worked with would have gone through all that.

If this is the way it's supposed to be done, how does one go about identifying the number of transactions? The book suggests using a spreadsheet with the following headers:

trans_type Number, Tot_entry_size, Avg_entry_size, largest_entry

Information on the transaction type obviously comes from knowing your database. Number of transactions, I would think, comes from the delta of writes from v$rollstat. Total entry size is the product of number and average or largest entry size. Where does the average and largest entry size come from?

Any info would be greatly appreciated.

Doug

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Douglas K. O'Leary
Senior System Administrator
dkoleary_at_mediaone.net