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Database Systems: Concepts, Design and Applications by S. K. Singh

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18.6. Concurrency Control in Distributed Databases

As we have discussed that the database of distribute system resides at several sites, control of data integrity becomes more problematic. Since data are distributed, the transaction activities may take place at a number of sites and it can be difficult to maintain a time ordering among actions. The concurrency control becomes difficult when two or more transactions are executing concurrently (at the same time) and both require access to the same data record in order to complete the processing.

Fig. 18.14. Final result by joining Y and S at site B

In a DDBS, there may be ...

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