How can I set PCTUSED and PCTFREE in Warehouse databases?

Question

Hi,
There are many Schemas in our database and some are used for OLTP and some others are used for Warehouse. Also our tablespaces are Local Managed.
Could you help me please how can I set PCTUSED and PCTFREE for Warehouses and OLTP.
What are your suggestions? What should be optimum?
DB version is 9.2.0.8.
thanks & regards

Answer 1

If you are using locally managed tablespaces with ASSM then the pctused parameter would no longer apply. In all cases dictionary vs locally managed with or without ASSM you should set pctfree based on how much of the data row column values are present at initial row insertion and how likely any column is upated to a larger size after initial row insertion.
In a warehouse I would expect most of the tables to have 100% of the row data present at initial insert and for the data to never be updated. For tables meeting this requirement a pctfree of 3 - 5% would likely be a good choice. I never like to use 0% since the day may come when you add another column to the table.
With OLTP tables the ideal pctfree value varies more from table to table. Most table so seem to work well enought with the default 10% but I have seen tables that need 50% pctfree to prevent row migration since only the key column values existed at initial insert and most all the other column data was added later.
Where ASSM is not in use I like to set pctused to 95 - pctfree. Over the last 15 years I am not sure I ever found a need to change the pctused from this once set. I have set a lot of tables up over the years from the old default of 40% to use 60% and 80% before resetting everything during a server platform migration as I mentioned above.
HTH -- Mark D Powell --