Within Toad under the DBA, Server Statistics, a warning message appears on Chained Fetch Ratio stating 'PCTFREE is too low for a table'.
Chained Fetch Ratio represents the number of times sessions attempting to read a row had to perform an additional read because the row had been chained to another block. This will occur when an update to a row causes the row length to increase but there is insufficient free space in the block for the expanded row.
The typical cause of chained rows is an inadequate value for PCTFREE, which is the amount of space within a block reserved for updates. You can find tables that contain chained rows with the ANALYZE TABLE command, which will store a count of the chained rows into the USER_TABLES view. Tables with chained rows may need to be rebuilt using a higher value for PCTFREE.
