物化视图,可以理解为保存master table 在过去某个时间点状态下所有数据的一个视图。其利用materialized view log或direct loader log(记录了物化视图自上次更新后的所有master table的更新记录)来reflash物化视图,也叫fast reflash.或者进行一次complete reflash,对物化视图进行重建。
注意:每个materrialized view log只会对应一个master table,而且其保存在master table中的同一个数据库和模式下。
根据ORACLE的技术文档,物化视图可以在下面三种情况中使用:
1、In data warehouses, you can use materialized views to compute and store data generated from aggregate functions such as sums and averages。
2、In materialized view replication , the view contains a complete or partial copy of a table from a single point in time. Material ized views replicate data at distributedsites and synchronize updates performed at several sites. This form of replication is suitable for environments such as fi eld sales when databases are not always connected to the network.
3、In mobile computing environments, you can use materialized views to download a data subset from central servers to mobi le clients, with periodic refreshes from the central servers and propagation of updates by clients to the central servers.
4、They can improve performance of SQL execution when used for query rewrite operations.
---------------------------------------------------------------------------------------------------
如有错误,欢迎指正
技术交流QQ:1732035211
技术交流邮箱:1732035211@qq.com
新浪微博:数据库小菜鸟http://weibo.com/u/3132578390