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6. data and lob are accessed separately( ie. data is read first, and SOMETIMES the lob is read)
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Can you define "SOMETIMES" in terms percentage?

If the percentage is around 5 to 10, then I would opt out-of-line LOB storage.

If data is going to be around 4K, you do not need LOB column, you can very well use varchar2.

Also, you can consider larger block size to store more rows in one block.

Tamil