Re: Oracle Internals (Overhead)

In article <34e094a4.2752401_at_news.santafe.edu>, Sid <pia_at_e_central.com> writes
>Hi All,
>
>I'm trying to do some sizing estimates for a project and need to know
>something about how Oracle stores its data:
>
>1) We have some fields that are unsigned integer values between 0 and
>255. Can Oracle store these in a single byte, or is there a 2-byte (or
>even a 4-byte) minimum for integers?
>

Oracle stores numbers as variable length data, the length depending on the number of significant digits. Values between 1 and 255 may take 2 or 3 bytes.

>2) What is the number of bytes required to store a Date field? Is
>this the same whether it's just a date or whether it's date with time
>information?

All Oracle date fields include time information and they take 7 bytes.

>3) If we have a varchar2 field, what is the number of overhead bytes
>required for the field length information (e.g. is it a two-byte
>length, a one-byte terminator, or something else)?

It is a length indicator. If the column is less than 255 then 1 byte otherwise 3.
>
>4) If we have a long raw field, what is the number of overhead bytes
>required to store the field?

Not sure, but since a long can be 2Gb, then I suspect it will be a 32 byte length.
>
>5) What is the number of overhead bytes per row stored in the
>database?
>
>Also, if anyone knows of a reference that has this type of info I'd
>appreciate it.

All this is in the Oracle server reference manual. I suggest you find out a bit more about Oracle before you start designing systems with it.
>
>TIA,
>
>Sid Gudes
>cougar_at_road_runner.com
>ANTI-SPAM: remove "_" after "road" when replying
 

-- 
Jim Smith