The Optimizer chooses Cost_based approach and optimizes with the goal of best throughput if statistics for atleast one of the tables accessed by the SQL statement exist in the data dictionary. Otherwise the OPTIMIZER chooses RULE_based approach.
Choosing an executing planbased on the access paths available and the ranks of these access paths.
A Transaction is a logical unit of work that comprises one or more SQL statements executed by a single user.
COMMIT makes permanent the changes resulting from all SQL statements in the transaction. The changes made by the SQL statements of a transaction become visible to other user sessions transactions that start only after transaction is committed.
The goal of the optimizer is to choose the most efficient way to execute a SQL statement.