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Transaction-Level Read Consistency (313)

原创 IT综合 作者:tsinglee 时间:2007-12-05 13:32:06 0 删除 编辑

Oracle also offers the option of enforcing transaction-level read consistency. When a
transaction runs in serializable mode, all data accesses reflect the state of the database
as of the time the transaction began. This means that the data seen by all queries
within the same transaction is consistent with respect to a single point in time, except
that queries made by a serializable transaction do see changes made by the transaction
itself. Transaction-level read consistency produces repeatable reads and does not
expose a query to phantoms.

事务级一致性读
1. 事务级一致性读 : 当事务运行在串行化模式下时 ,
则事务内所有数据访问的均是事务开始时的数据状态
即事务内的所有查询对某个时间点来说具备一致性
2. 事务级的读一致性能够保证可重复读取并可阻止出现幻象读取

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