Transaction isolation level is a conditional value that determines to what extent, as a result of logically parallel transactions in the DBMS, it is allowed to receive inconsistent data. The transaction isolation scale contains a range of values, ranked from lowest to highest; a higher level of isolation means better data consistency, but using it can reduce the number of physically concurrent transactions. Conversely, a lower level of isolation allows more concurrent transactions, but reduces the accuracy of the data. Thus, choosing the used level of isolation of transactions, the developer of the information system, to a certain extent, provides a choice between the speed of work and ensuring the guaranteed consistency of the data received from the system. Concurrent access issues using transactions With parallel execution of transactions, the following problems are possible: lost update - if one data block is simultaneously changed by different transactions, all changes are lost...
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