Does too many extents afftect database performance?

Hi gurus
There are some tablespaces created with "UNIFORM SIZE 1M" which should be created "SYSTEM" . The database version is 10g. I worry about that too much extents will affect the database performance even
availability cause extent management overhead. Do i need to recreate these tablespace with "SYSTEM" allocation type or just do nothing? Thank u for your reply!!
Edited by: KevinMao on Apr 12, 2009 8:48 PM

"SYSTEM" is for Tablespaces created with AUTOALLOCATE. Here you would have extents sizes beginning at 64K and then growing to 1M, 8M and 64M.
With "UNIFORM 1M" all your extents are 1M in size. If you have tables/indexes/partitions growing into the tens of GBs in size, you would have extent counts of tens of thousands. That, in itself, is not an issue.
"extent management overhead" that you refer to is actually reduced from DMT to LMT. Within LMT, the difference between "UNIFORM 1M" and "AUTOALLOCATE" may not be noticeable unless you have a particular patten of a very large number of DROP and TRUNCATEs being executed frequently. In that case, assuming that such DROP and TRUNCATEs are for small "temporary" tables, "UNIFORM 1M" may actually be better than AUTOALOCATE, except that you would be "wasting" some disk space (as the former would use 1M extents while the latter would use 64K extents for the first MB).
If you think of "AUTOALLOCATE"s 8M and 64M extents for very large tables, you might actually be better of using UNIFORM 32M or UNIFORM 64M for specific tablespaces and tables. Just be careful not to put relatively small tables into such tablespaces !
Edited by: Hemant K Chitale on Apr 13, 2009 11:58 AM

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