PCTUSED is a storage parameter in Oracle which specifies when a database block is empty enough for Oracle to add it to the free list.
When the percentage of used space in a block is greater than the PCTUSED parameter, Oracle will not add new rows to the block. The default settings for all Oracle tables are PCTUSED=40.
- PCTUSED is disregarded for all objects created in locally managed tablespaces when Automated Segment Space Management (ASSM) is enabled.
- PCTUSED is ignored for indexes: Oracle must manage the freelist re-link process for index tree management because the index node boundaries are the same as the index data block size.
Hence, PCTUSED is not used for index segments.
