COST-based optimiztion

From: Vsevolod Afanasjev <afanasjev_at_cse.unsw.edu.au>
Date: 1997/10/16
Message-ID: <344560B8.6995@cse.unsw.edu.au>#1/1

I cannot find information on cost-based optimization. Oracle Server Tuning manual, Advanced Oracle Tuning and Administration (Oracle Press), Oracle Tuning (Oracle Press), Oracle Tuning (O'Reilly) - all those books just say that it exists, it should be used, and how to use it, i.e. ANALYZE TABLE and OPTIMIZER_MODE, plus hints. That's almost all. I know that in 7.2, only the cost of the whole statement can be calculated, while in 7.3 the cost is given for each operation.

But how does Oracle calculate the cost? What is the formula? Does it somehow take into account memory available? Size of the SGA? DB_BLOCK_BUFFERS? DB_BLOCK_SIZE? It looks that the only way to use the cost-based optimization is "guess and try". Received on Thu Oct 16 1997 - 00:00:00 CDT