Abstract
Parallel execution of relational algebra operators can be performed on single computer, multi-programming or multi-tasking operating systems. 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 on the distributed database system environment, where each free operator executed in one specific location / computer (relatively to other free operator of transaction). Consequently, improvement of performance depend on : number of free operators of transaction, number of set of free operators, degree of freedom of operators, and data location relatively to the location where the operator executed.