PCT Free: PCT Free is used to denote the percentage of the free space that is to be left when creating a table. This parameter tells oracle how much space to leave in each oracle block for future updates. This defaults to 10. If table will have large number of updates, a larger value is needed. If the table will be static, small value can be used.
PCT Used: PCT Used is used to denote the percentage of the used space that is to be used when creating a table. This parameter tells oracle the minimum level of space in a block to maintain. Default is 40. A block becomes a candidate for updates if its storage falls below PCTUSED.
PCTUSED + PCTFREE should not exceed 100. A high PCTUSED value results in more efficient space utilization but higher overhead, as oracle must work harder to maintain the free block list.
eg.:: Pctfree 20, Pctused 40
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