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Choice of Isolation Level (326)

原创 ERP 作者:tsinglee 时间:2007-12-08 13:42:18 0 删除 编辑

Application designers and developers should choose an isolation level based on
application performance and consistency needs as well as application coding
requirements.

For environments with many concurrent users rapidly submitting transactions,
designers must assess transaction performance requirements in terms of the expected
transaction arrival rate and response time demands. Frequently, for high-performance
environments, the choice of isolation levels involves a trade-off between consistency
and concurrency.

Application logic that checks database consistency must take into account the fact that
reads do not block writes in either mode.

Oracle isolation modes provide high levels of consistency, concurrency, and
performance through the combination of row-level locking and Oracle’s multiversion
concurrency control system. Readers and writers do not block one another in Oracle.
Therefore, while queries still see consistent data, both read committed and serializable
isolation provide a high level of concurrency for high performance, without the need
for reading uncommitted data.

选择隔离级别
1. 在应用性能 , 一致性读要求 , 以及应用代码需求的基础上选择隔离级别
2. 在已提交读和串行化两种隔离模式下读操作都不会阻塞写操作

take into account 考虑

[@more@]

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