OBJECTS WITH MORE THAN 50% OF MAXEXTENTS NOTES:
Owner - Owner of the object
Tablespace Name - Name of the tablespace
Segment Name - Name of the segment
Segment Type - Type of segment
Size - Size of the object (bytes)
Extents - Current number of extents
Max Extents - Maximum extents for the segment
Percentage - Percentage of extents in use
As of v7.3.4, you can set MAXEXTENTS=UNLIMITED to avoid ORA-01631: max # extents (%s) reached in table $s.%s.
To calculate the MAXEXTENTS value on versions < 7.3.4 use the following equation: DBBLOCKSIZE / 16 - 7
Here are the MAXEXTENTS for common blocksizes: 1K=57, 2K=121, 4K=249, 8K=505, and 16K=1017
Multiple extents in and of themselves aren't bad. However, if you also have chained rows, this can hurt performance.