Re: Table with 300 columns (ie > 255) : Row Chaining ?

> I have some interesting findings when I retrieve a single row from a
> table with >255 columns (348 columns). For the table definition in
> my test case, if I fetch the 95th column or lower, I see 1
> "consistent gets" against the table. If I fetch the 96th column or
> higher (from the *same* row), I see 2 "consistent gets" .

This is probably because the split occurs between column 95 and 96. Do a block dump to check it... This is because the first row piece is not of "full length". In other words, the pieces are split and stored in "reverse order". For example, if you have a chained row that is stored in two blocks, not only the first column is stored in a block coming after the block containing the last row, but in addition the first piece is smaller than the second one. Go figure why...

HTH
Chris

Troubleshooting Oracle Performance, Apress 2008 http://top.antognini.ch

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