Parallel execution of relational algebra operator under distributed database systems

Parallel execution of relational algebra operators can be performed on single computer, multiprogramming or multitasking operating systems. In doing so, time response can be improved, compared to sequential execution, using concepts of: free operators, set of free operators, and degree of freedom of operators. Parallel execution of relational algebra operators introduced, using the concepts above, can be adapted to the distributed database system environment, where each free operator executed in one specific location/computer (relatively to the other free operator of the transaction). Consequently, improvement of performance depends on: the number of free operators of the transaction; the number of sets of free operators; degree of freedom of operators; and data location relatively to the location where the operator executed.