Re: Sizing Rollback and Temporary Segments

uidixon!idixon_at_infocom.co.uk (Ian Dixon) writes:

> I'm about to set up Oracle on another machine and I thought that this
> time it would be nice to get the rollback and temporary segments at
> the right size to start with. Unfortunately I cant find any mention
> in the manuals about how I should do this. Can anyone offer any
> suggestions?

The temporary segments will be roughly the size of your largest index, because they are created when indexes are built. Other than that, they may be used to store portions of sort runs (during queries) that do not fit into memory. If you sort an entire large table and the table is larger than the number of blocks in the SGA, it will overflow to temporary segments.

The rollback segments will be the size of your largest transaction; if you delete an entire table, the active rollback segment will grow to roughly that size. (if you drop or truncate a table, this does not occur since rollback is out of the question). same goes for updates or inserts. this is just a rule of thumb: the data in the rbs may be more compact than its original image in the table.

Better to estimate based on some knowledge of the application's behavior, then over-allocate by your favorite fudge factor.

--
Dave Mausner / Sr Consultant / Datalogics division of Frame Technology Inc
441 W Huron / Chicago IL 60610 / +1-312-266-4450 / "Just show me the code"