What is a free list?
What is a free list?
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A free list is a data structure that stores the address of data blocks that have been allocated to the extents of the associated segment and have sufficient free space to accommodate new inserts into the segment. Whenever an insert operation is being performed on the segment, Oracle checks the free list for the availability of data blocks to accommodate the insert operation (this is gauged from the value of PCTUSED). If Oracle finds sufficient space within the available data blocks, the insert operation is successfully completed. However, if it finds that the space within an available data block is not sufficient to accommodate the insert operation, then that data block is taken off the free list and the insert operation goes into a wait list. This insert operation can only be performed when data blocks with sufficient free space are again available with the free list. Oracle can maintain one or more free lists for a segment. Generally, having more than one free list is considered better for performing concurrent inserts.
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