From Oracle FAQ
Each segment has one or more freelist (in the segment header) that keeps track of data blocks under the high-water mark.
When records are inserted into the segment, Oracle examines the freelist to determine which data blocks have available space to store the new rows. When rows are deleted (or updated), and the amount of free space in the data block falls below a threshold value (PCTUSED), the data block will be returned to the freelist.
Freelists and freelist groups are ignored when using ASSM. Starting from Oracle 9i, ASSM is preferred.
CREATE TABLE tab1 (col1 NUMBER) STORAGE (FREELISTS 10);
- ASSM - Automatic Segment Space Management
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