Optimizer not choosing the lower cost plan in 11.2.0.3.5
Hi,
We have just upgrade from 10.2.0.4 to 11.2.0.3.5 EE, in Linux 5 64 bits.
After that, some sql are slower.
When we gather the execution plan information from the awrsqrpt.sql , we see that Oracle has generated 2 plans for these sql.
One is Full Table Scan biased, with a higher cost and another plan is index biased, with a lower cost.
The optimizer started with the Index biased lower cost plan but always ends up choosing the one with FULL table scan and then stick with it.
I have tried the optimizer_index_caching and optimizer_index_cost_adj, but the optimizer stick to the FULL table scan plan.
We have just upgrade from 10.2.0.4 to 11.2.0.3.5 EE, in Linux 5 64 bits.
After that, some sql are slower.
When we gather the execution plan information from the awrsqrpt.sql , we see that Oracle has generated 2 plans for these sql.
One is Full Table Scan biased, with a higher cost and another plan is index biased, with a lower cost.
The optimizer started with the Index biased lower cost plan but always ends up choosing the one with FULL table scan and then stick with it.
I have tried the optimizer_index_caching and optimizer_index_cost_adj, but the optimizer stick to the FULL table scan plan.
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