How many users/ schemas can we create in an oracle database?

Question

How many users can we create in an oracle database? Or how many users can oracle handle?
Problem-
I have to store information of ontologies (I will use countries instead) in db.
I have to store information regarding countries.
I have 13 tables in all to maintain for each country.
Now there are two approaches:
1) keep only 13 tables. Have an extra column in each table to indicate that a particular
row stores information for which country.
2) create a new user/ schema for each country. So we can get rid of the extra column
needed in 1st approach.
I have used the second approach. This is because number of entries in each table for a
given country will be large.
So initially when the s/w is installed I create a central-user. Each time data for new
country has to be entered central-user creates a user/ schema, and creates tables for
this user/ schema. The central user can access the tables of all the countries by
country_name.table_name. By this approach I believe searching would be easy.
If there is any flaw in my approach kindly mention it.
Thank you

Answer 1

There is no (practical at least) limit to the number of users & schemas you can have in Oracle.
Your approach, however, is not going to scale nearly as well as the first option you outlined (adding a column). You are going to end up caching every possible variation of the various queries you're going to be executing because you will be referring to so many different tables, which is going to mean that you are doing a lot more work to parsing statements and generally churning through the shared pool. If you create enough users, you're liable to start hitting ORA-04030 errors because your shared pool is so fragmented.
Additionally, you're likely going to end up with a whole lot of dynamically generated SQL to accommodate new schemas getting added over time which is going to cause you even more pain. Figuring out dynamically what table to join in is a heck of a lot more difficult for the programmer to write and for the database to handle than simply passing in a different country code.
If you're concerned about having too much data, you can have your cake and eat it to by adding the country column and partitioning the tables based on country.
Justin
One other item I forgot to mention is maintainability. Having dozens or hundreds of "identical" schemas makes maintenance a huge pain because something like adding a new column now requires dozens or hundreds of separate DDL statements. You're almost guaranteed that some schema isn't going to be in sync-- it's going to miss a column or miss an index, etc.
Message was edited by:
Justin Cave