threading in the databases

I would like to know what does it mean if some one says that a database is single threaded? And what does it mean if a database is multi threaded?

I understood it as multiple users can query a mult开发者_StackOverflow社区i threaded database and it is not possible in single threaded database.Or if there is other fundamental difference? Can some one explain?

Thanks in anticipation

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It is not about how users connect to the database is about the number of operations, either to assert or query data that can be performed at the same time. Single-threaded means that only one user-operation can be run at the same time. Multi-threaded means there are multiple threads to run multiple operations at the same time and the database system has been designed in such a way that is able to control race conditions and locks between records to allow consistency according to the ACID principles.