Re: How can I estimate the size necessary for archive log files ?

There are no good formulae that I know of. Deletes and Inserts will tend to be the entire row length plus some overhead, updates just the length of the columns being updated. But add in rollback and indexes, and things get much stickier, and there's no magic formula for working it out ahead of time.

You can do a 'sample' transaction in SQL Plus having first done a 'set autotrace trace', and that will show you how much redo that specific statement caused to be generated. A different technique is available from my site (under backup and recovery tips, strangely... an article entitled 'what exactly happens when you put a tablespace into hot backup mode?' (or something similar!)), but that again presumes you can actually fire off some test transactions. (My version is different from SQL Plus's because it has to deal with the fact that even 2 bytes of redo have to occupy an entire O/S block in the redo logs... what's generated and what it occupies on disk is/can be different).

You can add in index key field lengths, and make an allowance for them. You can add in a fudge factor for rollbacks. But it's all going to be pretty messy.

Maybe Tom has something more precise?

Regards
HJR

--
----------------------------------------------
Resources for Oracle: http://www.hjrdba.com
===============================


"Frederic Payant" <fpayant_at_club-internet.fr> wrote in message
news:u2sv7u0cvt4i509prtca37k9pj7rvvf04q_at_4ax.com...


> I apologize but I ask an ambiguous question.

>

> What I would like to calculate is the volume of _online_redo_log that

> my database will generate when installed.

> (I made a confusion between archive logs and redo log)

>

> The actual ativity is not representative as we are in development and

> our core product in a software on which we do not have many

> visibility.

>

> I must find what volume of data will be generated in redolog files,

> assuming that I can estimate how many rows and of which size will be

> inserted/deleted/updated.

> I suppose that because of indexes and all this sort of things, size of

> redolog will not be the sum of all these updates.

>

> But is there any formula who could permit me to estimate this size ?

>

> Any advise will be apreciated

>

> Thanks by advance

>

>

> Amicalement

> Frédéric PAYANT