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Facts about Very Large Databases (VLDB)

Kings Canyon Sunset QUESTIONS :
  1. How can I get good performance out of a Very Large Database for a Library ?

This Section was produced in reponse to a Question posed on
and discusses the situation where a central library database of books.
The original Question was :-

The Database holds details of 10,000 different community libraries, 
each with 10,000 books (more or less). 
The central DB is updated daily.

Should I:

Have 10,000 tables, one for each library..
or have one table with 
10,000 (libraries) * 10,000 (books) = 100,000,000 rows?

Anytime a search is performed the DB would 
a) Have to perform 10,000 queries (one on each table) or,
b) just one query, run on 100,000,000 rows.

My answer was ...

Your problem is how to implement a Very Large Database,("VLDB"), or Data Warehouse.

I have a page on my Web Site devoted to FAQs on Data Warehousing, called  dw_facts.htm.

The specific question you have to answer is :-
"How do I split up the data to optimise its distribution and retrieval".
This is a lengthy answer, so for the moment, I'll ignore the aspect of updating.

The problem and approach is general but the solution will be vendor-specific.

The vendor that I would recommend is Oracle, ( because they 
have done a lot of work in this area. There are also specialist vendors,such as 
Redbrick,(, but they tend to be more expensive,and there is 
Microsoft, with their OLEDB inititiave, but your first stop should be to check out Oracle.

Specifically, techniques you are looking for include :-
a) distributed databases
b) parallel servers, so that a retrieval can be done in parallel streams
and accomplished faster.
c) indexing, particularly bitmap indexing. 
If you are dealing with text, look at Oracle Context text retrieval product.
d) clustering, which is co-locating groups of data that are often retrieved together.
e) vertical and horizontal segmentation. 
These are techniques for splitting up the data according to values.
For example, into regional groups,(horizontal rows), or different data items,(vertical).

An excellent book, which describes all of these techniques, is :
"Oracle Data Warehousing Unleashed', by Bonnie O'Neill et al,published by SAMS, and ISBN is 0-672-31077-5.
available at Amazon for $49.99 :-

These are the Steps you should follow :-
Step 1) Identify patterns in retrieval of the data.
Step 2) Look for patterns that you can exploit in distributing the data. Start by 
thinking in terms of about 20 Databases with 500,000 records in each one.
Step 3) Evaluate the relevance of techniques a) to e) above.

If you have an appropriate budget, you can call in Oracle to give you recommendations.
If not, it will be difficult for you to make progress unless you have technical expertise available.

If you are able to complete these Steps, then you will have a definition of the problem, and one 
vendor-specific solution, which you can use as a benchmark for to compare against other vendor solutions.

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