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>He is going through a worksheet and some Implementation guides and is
>coming up with about 1 Tb and over 1000 unique tables.
I have no idea what the calculations in that sizing guide look like.
One of the questions to ask is how the sizes add up to 1 TB; e.g. is
this something like: you'll have these 1000 tables and they all be
around 1 GB if you have 100 000 customers. So what I'm driving at: the
calculations may become inacurate the bigger the application gets.
Keep in mind: this is just wild speculation on my side.
>Now, from what I hear, each Oracle table will get at least one DRD (the
>maximum size of DRD that Oracle use being 14 Gb).
Where did you get that from? I mean the table/drd mapping. Two comments
here:
1) Yes there are limits within Oracle for the maximum size of a
datafile. I can't remember the exact formula but the max datafile
size depends on the Oracle block size. And the absolut maximum of
14GB sounds about right.
2) Oracle tables are allocated in so called extends. One table can have
several extends up to a limit. All extends of one table must be
allocated in one tablespace (this limitation exists in Oracle7). A
tablespace can hold any number of tables. A tablespace comprises 1
or more datafiles of any kind (raw, UFS, AdvFs) and size.
So there may be a recommendation to put each table in a seperate
tablepace for performance reasons but there is no strict rule to
that and its also a pretty unusual approach with any larger number
of tables.
As an approch to the other extreme you may decide to throw all
your drds into one single tablespace and allocate extends for all
1000 tables there.
So if you have to build a 1 TB database you only need 74 drds (74 *
14GB > 1 TB). You may want to use more for better control over which
table goes onto which disk.
Martin
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