What's the best practice to partition an existing table?

We are using Oracle 11g EE 11.2.0.3.0. We want to partition an existing table. I found some information from this link [http://www.oracle-base.com/articles/misc/partitioning-an-existing-table.php], but I am not sure whether that's the best way. Could anyone share the best practice of partitioning an existing table?
Thanks.
Jun

>
We want to partition a few related tables. A couple of tables have about 30 million rows, and a couple of other tables have about 10 million rows. The data for those tables is for ~2000 accounts, each of them is identified by a column named "account_id". We want to partition the tables by using the "account_id" as the partition key to gain better performance for queries, so we would probably use hash partition. Please advise.
>
1. What evidence do you have that your performance will be any better if you partition those tables?
2. What evidence do you have that there is anything wrong with the performance of your current queries?
3. Have you reviewed the actual execution plans for your most important queries to see if there is even any room for improvement?
If your query uses account_id as a predicate but only pulls a few records from a 'master' table for that key value your performance may actually be worse if you partition that table. That is because using an index range scan Oracle can easily find the ROWIDs of the rows that need to be selected and then easily retrieve them regardless of their physical location.
If you have queries that do NOT use account_id but currently use indexes the performance of those queries may also be worse if you partition that table. Those indexes will be GLOBAL.
There are two major implications when you use hash partitioning:
1. Any query that does NOT include the partitioning key (account_id for your case) will, of necessity, have to use a full table scan if an appropriate index is not available.
2. You will get NO management benefits such as being able to add/remove partitions that include old data.
Before you decide to partition a table you should conduct tests and examine the execution plans for your important queries.

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