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One of the most popular systems of simulation - GPSS World provides users (1) software tools to interact with the system in the process of simulation research and (2) software tools, realizing immediately the implementation of the model (including: syntax analyzer interpreter model, clock modeling, management of the list of events and more.). Until a few years ago the programs in the first group only automated a part of research itself, namely the creation of a text model and conduct experiments with it. In the ab...

The method of two-phase locking (2PL) is still used in concurrency access in the global transaction management. It has its advantages in distributed database management systems (DDBMS), conflicted events. The paper views modeling algorithms of Centralized, Distributed and Primary copy Two-version Two-phase locking. The presented algorithms are models of the corresponding variants of the 2PL protocols for DDBMS using two versions. As in concurrency control of distributed transactions in DDBMS deadlocks are possible...