Significance of Initial (intial_extent)parameter while creation of table

Question

Hi All,
I am designing a new schema for my 10g database and I am in process of creation of tablespaces and tables.
My Tablespace are extent management local autoallocate and auto segment space management.
With “segment space management Auto”, I understand that I don’t have to define storage clause in tablespace and freelist will be taken care by bitmap
My question is
while creation of tables what’s the significance of Intial (intial_extent in user_tables) parameter.?
Do I need to consider this parameter while defining large and small tables?
Is this not controlled by “auto segment space management.” Parameter of tablespace.?

Answer 1

While it is unlikely to make a measurable impact on anything in practice, it is almost always preferable in theory, assuming perfect knowledge of the system, to have a few different tablespaces with different uniform extent sizes and to put each object in the appropriate tablespace for its size (i.e. giant tables in the tablespace with giant extent sizes, tiny tables in the tablespace with tiny extent sizes, etc.). The problem with this, however, is that you very rarely have perfect knowledge in advance about object sizes and growth and size patterns are likely to evolve over the life of the system, so you can suck up a great deal of DBA and developer time gathering and maintaining this sort of information as well as responding to changes over time (i.e. moving objects from one tablespace to another as their usage patterns change). For most systems, the potential benefit to having a perfect setup, rather than putting everything in an AUTOALLOCATE tablespace, is far smaller than the cost of actually doing so.
Unless you have some reason to believe that your application is in the minority where squeezing the last bit of storage efficiency is worth the hassle, I'd tend to suggest throwing everything in an AUTOALLOCATE tablespace.
Justin